* Put generated files to disk:
- Add new command line param 'GeneratedFilesOut'
- Route new param through tasks with defaults
- Write out generated files when requested to do so
- Rationalize post generation to avoid uncesseary work
- Add Tests for targets and emit
- Add test to track the fact that we can overwrite files on windows in SxS cases

* Records: Warn if Equals or GetHashCode is redefined, but not both

* Fix ErrorFacts.Generated.cs

* Apply feedback from @jcouv

* Fix RecordTests.cs due to new warnings - part 1

* Small fix

* Small fixes

* Fix RecordTests.cs due to new warning - part 2

* Fix formatting

* Fix RecodTests.cs due to new warning - part 3

* Fix RecodTests.cs due to new warning - part 4

* Fix RecodTests.cs due to new warning - part 5

* Fix RecodTests.cs due to new warning - part 6

* Fix an unintentional mistake

* Apply feedback

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs

* Apply feedback

* Feedback

* UpdateXlf

* Update DiagnosticTest.cs

* Update RecordTests.cs

* Update WarningLevel to 3

* Fix test: warning level

* Allow record's `parameter_list` to be empty.

Related to #47091
https://github.com/dotnet/csharplang/blob/master/meetings/2020/LDM-2020-08-24.md#base-calls-on-parameterless-records
https://github.com/dotnet/csharplang/pull/3900

Restrict readonly from being applied directly to init accessors, and prevent them from being considered readonly by the language.

* Use a distinct diagnostic ID when an exhaustiveness report uses an unnamed enum value.
Fixes #47066

* Handle additional cases of Main and ModuleInitializer methods
* Simplify UnmanagedCallersOnlyAttributeData
* Reword errors and add additional clarifying error for delegate conversions.
* Add additional suggested test cases.

We will now issue diagnostics when methods attributed with
UnmanagedCallersOnly are called directly, or converted to delegates. We
will also mark methods imported from metadata with these attributes on
unsupported member types as unsupported by C#.

Co-authored-by: NManish Vasani <mavasani@microsoft.com>
Co-authored-by: NAndrew Hall <ryzngard@live.com>
Co-authored-by: NFred Silberberg <frsilb@microsoft.com>
Co-authored-by: NSam Harwell <sam@tunnelvisionlabs.com>
Co-authored-by: NJason Malinowski <jason@jason-m.com>
Co-authored-by: NTomas Matousek <tomat@microsoft.com>
Co-authored-by: NCyrus Najmabadi <cyrus.najmabadi@gmail.com>
Co-authored-by: NJason Malinowski <jason.malinowski@microsoft.com>
Co-authored-by: NSam Harwell <Sam.Harwell@microsoft.com>
Co-authored-by: NDavid Barbet <dabarbet@microsoft.com>
Co-authored-by: Nmsftbot[bot] <48340428+msftbot[bot]@users.noreply.github.com>
Co-authored-by: NNeal Gafter <neal.gafter@microsoft.com>
Co-authored-by: NYoussef Victor <31348972+Youssef1313@users.noreply.github.com>
Co-authored-by: NTomáš Matoušek <tmat@users.noreply.github.com>
Co-authored-by: NRikki Gibson <rigibson@microsoft.com>
Co-authored-by: NFredric Silberberg <frsilb@microsoft.com>
Co-authored-by: NBen Lichtman <belichtm@microsoft.com>
Co-authored-by: NBen Lichtman <uniqueiniquity@users.noreply.github.com>
Co-authored-by: NChris Sienkiewicz <chsienki@microsoft.com>
Co-authored-by: NAllison Chou <allichou@microsoft.com>
Co-authored-by: NDavid Wengier <david.wengier@microsoft.com>
Co-authored-by: NDavid Maas <contact@pathogenstudios.com>
Co-authored-by: NDavid Wengier <dawengie@microsoft.com>
Co-authored-by: NShen Chen <cos_ifne@hotmail.com>
Co-authored-by: NShyam Namboodiripad <gnamboo@microsoft.com>
Co-authored-by: NShen Chen <Cosifne@users.noreply.github.com>
Co-authored-by: NJulien Couvreur <jcouv@users.noreply.github.com>
Co-authored-by: NDavid Wengier <git@wengier.com>
Co-authored-by: NMarco Goertz <mgoertz@microsoft.com>
Co-authored-by: NCharles Stoner <chucks@microsoft.com>

Allow `UnmanagedWithGenerics` parameter/return types, and mark the usage invalid in types with generic parameters.

Clarify UnmanagedCallersOnly requirements to be no type parameters, and all parameter/return types must be truly unmanaged.

Co-authored-by: NSam Harwell <sam@tunnelvisionlabs.com>
Co-authored-by: NManish Vasani <mavasani@microsoft.com>
Co-authored-by: NDavid Barbet <dabarbet@microsoft.com>
Co-authored-by: NJoey Robichaud <jorobich@microsoft.com>
Co-authored-by: NCyrus Najmabadi <cyrus.najmabadi@gmail.com>
Co-authored-by: NDavid Wengier <david.wengier@microsoft.com>
Co-authored-by: NShen Chen <cos_ifne@hotmail.com>
Co-authored-by: Nmsftbot[bot] <48340428+msftbot[bot]@users.noreply.github.com>
Co-authored-by: NSam Harwell <Sam.Harwell@microsoft.com>
Co-authored-by: NFredric Silberberg <frsilb@microsoft.com>
Co-authored-by: NGen Lu <gel@microsoft.com>
Co-authored-by: NPetr Onderka <gsvick@gmail.com>
Co-authored-by: NTomáš Matoušek <tmat@users.noreply.github.com>
Co-authored-by: NYoussef Victor <31348972+Youssef1313@users.noreply.github.com>
Co-authored-by: NCristiano Suzuki <crsuzuki@microsoft.com>
Co-authored-by: NRikki Gibson <rigibson@microsoft.com>
Co-authored-by: NJoey Robichaud <joseph.robichaud@microsoft.com>
Co-authored-by: NYair Halberstadt <yairhalberstadt@gmail.com>
Co-authored-by: NAllison Chou <allichou@microsoft.com>
Co-authored-by: Nmeziantou <meziantou@live.fr>
Co-authored-by: NVritant Bhardwaj <vrbhardw@microsoft.com>
Co-authored-by: NJulien Couvreur <jcouv@users.noreply.github.com>
Co-authored-by: NShen Chen <shech@microsoft.com>
Co-authored-by: NShen Chen <Cosifne@users.noreply.github.com>
Co-authored-by: NChris Sienkiewicz <chsienki@microsoft.com>
Co-authored-by: NJinu <jinuj@microsoft.com>
Co-authored-by: NMarius Ungureanu <therzok@gmail.com>
Co-authored-by: NJason Malinowski <jason.malinowski@microsoft.com>
Co-authored-by: NBen Lichtman <belichtm@microsoft.com>
Co-authored-by: NBen Lichtman <uniqueiniquity@users.noreply.github.com>
Co-authored-by: NDavid Wengier <dawengie@microsoft.com>

The native compiler had a bug here that permitted static classes to be used in parameter or return types for methods defined in an interface. We will now warn about doing this when warning waves are on.

We now error when a signature that is not compatible with UnmanagedCallersOnly is used. Specifically, these requirements are:
* The method must be static.
* The method must be ordinary, or a local function.
* The method must use only unmanaged types in its parameters and return type.
* The set of valid types passed to the `CallConv` property is the same as the set of types considered calling convention modifiers for function pointers.