Implements GetDeclaredSymbol for tuple literals and GetSymbolInfo for elements of tuple literals.

Merge dev15-rc3 into master

Enable override completion to use expression body accessors

Disallow Rename Tracking on named tuple elements (to match Inline Rename and prevent a crash)

The subsumption tree must treat an unconstrained type parameter as possibly null.
Also, if a previous case pattern handles all non-null input, any further case type pattern is subsumed.
Fixes #16688
Fixes #16671

Fixes #16559

Fixes #10765

They were building as 64-bit only since there wasn't a 32-bit CoreCLR before.

Small builds changes for end to end source build

Couple of infrastructure updates

added unit test

The VsdConfig.targets file was not located in our core targets location.
Moving there as this is the appropriate place for all targets / props
files in our build.

Additionally changed it to use the vsdconfig from our NuGet packages
directory instead of hard coding Visual Studio.

Properly detect and handle delegate relaxations when ByRef returns are involved.

Disable some of our analyzers from running on generated code files.

Fixes #15971

Singular is used in other parts of the repository already.

Attributes will not be permitted on type parameters or parameters of
local functions. This matches the existing behavior for the return type
and symbol itself, neither of which allow attributes to be applied to
them.

Fixes #1640

make telemetry to only log when there are multiple files re-analyzed

add support for StrongNameProvider for LUT.

In cases where there's no process to kill, TaskKill will write a
message with the words "ERROR:" to standard error. This will cause
MSBuild (when invoking cibuild.cmd as part of a composed build) to
think that the Roslyn sub-build failed.

Fixes #16334

Fixes
https://devdiv.visualstudio.com/DevDiv/_workitems?_a=edit&id=371205

this support wasn't there before since code lens nor solution analysis requires it.

* Harden compiler against exceptions during stream dispose

It's possible (likely even) for one of the streams the compiler uses for
output files will throw during disposal. Currently this crashes the
compiler. This change adds a wrapper type around stream to catch
exceptions during disposal and report them as diagnostics instead.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems?id=217719

* Add VB tests

* Respond to PR comments

* Respond to PR comments

* Respond to PR comments

* Conform to style guidelines

Fix overlapping diagnostic ids

Disable 'Rename File' if we're in a CPS project.

Fixes #16546

Be resilient to not having a containing type for a backing field.

Be resilient to getting an empty list of diagnostics when fixing all.

Fixes #15999