* Add definition of hostfxr_get_dotnet_environment_info_fn to hostfxr.h.

* Move doc for hostfxr_get_dotnet_environment_info into hostfxr.h.

Co-authored-by: NElinor Fung <elfung@microsoft.com>

* Move corehost under src/native

* Move content out of cli/ directory

* Update configurations post-move

* Update docs

* Add hostfxr_get_dotnet_environment_info

* Change access modifiers in structs

* Remove unnecessary context local

* Use global install location if no dotnet_root is specified

* Add framework tests

* Update framework_info comparison

* Remove commented code

* Remove unnecessary marshaling
Export fn

* Add hostfxr_get_dotnet_environment_info to hostfxr exports

* Fail if result is nullptr
Validate size of structs
Test that result_context isn't modified

* Remove version_as_str
Update tests

* Add tests for invalid args

* Single-File: Process bundles in the framework

This change implements the host changes proposed in the [design](https://github.com/dotnet/designs/blob/master/accepted/2020/single-file/design.md#startup)

The main changes for single-file bundles are:
* Bundle processing code is moved from apphost to hostpolicy
* HostFxr and HostPolicy process deps.json and runtimeconfig.json files directly from the bundle.
* HostPolicy performs verification wrt deps.json based on the contents of the single-file bundle.
* AppContext.BaseDirectory is set as explained [here](https://github.com/dotnet/designs/blob/master/accepted/2020/single-file/design.md#appcontextbasedirectory)

Currently, all files except deps.json and runtimeconfig.json are extracted to disk.
Once the runtime is able to processing assemblies directly from the bundle, they will no longer be extracted.

Notable details:
* The bundle driver (formarly runner.cpp) is divided into two parts:
   * bundle::info which describes basic information about the bundle available from the headers only
   * bundle::runner which has information about all embedded files, and the ability to drive extraction
  This facilitates linking only parts of the bundle handling code with hostfxr, while all code is linked with hostpolicy.
* The AppHost only links with bundle_marker to identify itself as a single-file bundle.
* If the AppHost is a single-file bundle, it notifies hostfxr using the new hostfxr_main_bundle_startup_info() API
* The HostFxr comminucates the single-file-information with HostPolicy using the host_interface_t structure.

Fixes https://github.com/dotnet/runtime/issues/32821

- Make hostfxr.h compilable in C
- Add hostpolicy.h and coreclr_delegates.h

Commit migrated from https://github.com/dotnet/core-setup/commit/988b3d3960383e8c56408c05160c8e12042420f0

* Add load_assembly_and_get_function_pointer to delegate type enum
* Add tests (commented out) with for calling delegates in a component


Commit migrated from https://github.com/dotnet/core-setup/commit/f7f4b1b0f0d83f9cffe7218a94de726c59514a77

Commit migrated from https://github.com/dotnet/core-setup/commit/aec6c77a664561249ecf763a642c6429c7891cdd

Commit migrated from https://github.com/dotnet/core-setup/commit/5b1d47b8487b1985f3ed2b3731ce828b8b9118ba

- Track existing hostpolicy_context in hostpolicy
- Add host_context to hostfxr to represent active (first) and secondary contexts
- Switch com/ijw/winrt hosts to use host context-based APIs
- Update nativehost test executable to exercise new APIs
- Make non-context-based entry points check for existing context and create an empty context
- Basic automated tests for context-based entry points

Commit migrated from https://github.com/dotnet/core-setup/commit/4f7fefe81748bcf7fe65ad3492ed2ca22a2b834a

Implement a WinRT host for .NET Core so users can write WinRT WinMDs that target and build on .NET Core.

We can't accurately test this E2E in CI until we have a test machine running a version of Windows with the Reg-Free WinRT support (requires at least Windows 10 19H1 Build 18309).

Runtime side of the host work is in dotnet/coreclrdotnet/core-setup#23402



Commit migrated from https://github.com/dotnet/core-setup/commit/4ed031a6a01352696bd7fdd58bddc365d34e91bf

Commit migrated from https://github.com/dotnet/core-setup/commit/18780678da576d8c629066f50af30159a8859b2f

* First pass porting mscoree/mscoreei's IJW hosting hooks into a new .NET Core host. Functions that use runtime data structures are stubbed out.

* Use Windows heap functions for allocating executable memory.

* Add IJW activation design document.

* Add talking point about loading dependencies from *.deps.json* files and what work needs to be done for those.

* Clean up design doc.

* Update design doc.

* Feedback.

* Clean up the PEDecoder since we don't need to port over all of the validation, just enough to ensure that the assembly is a .NET assembly.

* The OS will verify that the IJW image and the IJW host are the same architecture, so we don't need to branch on architecture.

* Clean up ijwhost and PEDecoder code based on review feedback.

* Refactor corehost.cpp and add implementations of functions to fetch IJW delegates from hostfxr.

* Move hostfxr resolution into separate file and make corehost only relevant for the exe hosts.

* Make get_latest_fxr local to fxr_resolver.cpp

* Implement fxr wire-up for ijwhost.

* Rvas are already mapped for loaded images.

* Don't use stubs if being loaded into currently running runtime.

* Update IJW activation doc based on updated info about callbacks.

* Implement token resolution from thunks. Fix calling a users native entry-point from _CorDllMain.

* Correctly resolve side-by-side hostfxr from ijwhost and comhost. Correctly handle an empty TPA when appending S.P.CL. Pass app-path to delegate.

* Update design doc.

* Remove unneeded validation.

* Fix assembler selection for ARM/ARM64.

* Fix indentation.

* Remove dead code in PEDecoder.

* Fix missing CommandLineToArgvW symbol in arm/arm64 builds.

* Fix ARM/ARM64 build by bringing over custom arm assembler supporting cmake from coreclr.

* Remove IJWBootstrapThunk opaque class. Rename all non-exported apis to match the snake_case convention in this repo.

* Remove exports.cpp files per pr feedback.

* Use an enum to specify which delegate to load from the runtime in the hostfxr<->hostpolicy API.

* Fix x86 build

* Make x86 implementation of get_thunk_from_cookie clearer.

* Symbol export changes needed for x86 as found by testing.

* Remove ijw-exe-specific path.

* clean up ijwhost.cpp since we only have one entrypoint into hostfxr from ijwhost now.

* Use enum for delegate getter in hostfxr-exposed api as well.

* PR Feedback.

* Add ijwhost to Microsoft.NetCore.DotNetAppHost package.

* Setup tracing on comhost and ijwhost entry points.

* PR Feedback.

* Remove IsILOnly checks.

* Clean up design doc.

* More cleanup on IJW activation design doc

* swallow tracing on IJW. Remove as much of corhdr.h as possible.

* Fix bad copy-paste in the install command in ijwhost cmake script.

* Fix cmake

* Add error message to trace for failure to find the "corehost_get_coreclr_delegate" entrypoint.

* Sign ijwhost. Fixes dotnet/core-setup#5485.


Commit migrated from https://github.com/dotnet/core-setup/commit/bc7bcc646567a261c0ae113d5fe43f17469af4ae