Enable DeadCodeAnalysis rules and address design/review feedback.

Fix race in SourceParameterSymbol

Log information about crashes during integration tests

Address PR feedback (use static ctor and remove regions) and also fix an assert seen during dogfooding.

Primarily addresses https://github.com/dotnet/roslyn/issues/29519#issuecomment-420067012

```
1. Enable the rules be default
2. Remove all the workaround/hacks for disabling the rules for product and enabling for tests.
3. Address offline feedback from @sharwell about avoiding deriving the tests from `TestBase`.
4. Separate out the pending non-design related work items from first comment into separate issues.
```

For 4., I have repurposed https://github.com/dotnet/roslyn/issues/29519 to track the pending issues with checkboxes in the first issue comment.

Add codesstyle, fix and refactoring for "Use Expression/Block body for lambda".

 Integrate elseless-if handling for 'invert-if' refactoring

Stop generating redundant this() when initializing struct property

We are not currently using this analyzer to its full extent since it
requires repository-specific configuration which is not yet provided for
Roslyn. Issue #29275 tracks configuring and enabling this analyzer.

Re-enable VB semantic / emit tests on Linux

* Move xunit package references to Roslyn.Toolsets.Xunit.targets

* Remove dependency on Microsoft.NET.Test.Sdk

This type, and it's children, had the same race condition around
attributes that `SourceEventSymbol` did. After some thought I decided to
move this code back into `SourceCompletionState` with a new name to make
it clear the completion is around attributes only.

This is a follow up to #29807

Fix race in SourceEventSymbol.GetAttributesBag

Add Make Field Readonly test for accessed fields

VB - fix broken code generated when converting to auto property

Prevent Format String analyzer from crashing on a local function named Format

There is a race condition around the setting of
`CompletionPart.Attributes` in `SourceEventSymbol`. This can be exposed
when the following execution pattern occurs:

- Thread1: Calls `GetAttributesBag` and pauses execution on the line `
`DeclaringCompilation.SymbolDeclaredEvent(this)`
- Thread2: Calls `ForceComplete` which will unconditionally call
`state.NotePartComplete(CompletionPart.Attributes)`
- Thread1: Resumes and hits an assert because `NotePartComplete` returns
`false`.

The root problem here is the unconditional call of `NotePartComplete`
inside of `ForceComplete`. The pattern in all of our other symbols for
`ForceComplete` is the following:

- Call `GetAttributes`
- Call `SpinWaitComplete(CompletionPart.Attributes, cancellationToken)`

This ensures that `NotePartComplete` is executed on the thread which
actually completes the loading of attributes.

As a part of fixing this I looked through all other uses of
`NotePartComplete(CompletionPart.Attributes)` to ensure they didn't have
this problem. Checked VB as well and it doesn't seem to have this issue.

Struggled to find a good way to test this as it's a race condition.
Given the high number of bugs we've recently filed on this assert I'm
confident we have the indirect coverage in our suites.

closes #28954

* Rename target GetBuildVersion to GetVsixVersion

* Targets refactoring to align with Arcade SDK

* Remove unused property

* Use Arcade VSIX build targets

* Upload Willow VSIXes directly from VSSetup directory

* Add setup packages to Roslyn.sln

* Remove swr validation from BuildBoss

* Avoid copying CoreXT packages

* Don't delete DevDivPackages\Roslyn dir

* Upload vsixes even when the build fails

* Clean up VSIX project files

* Install VSIXes in specified order

* Do not set TargetFrameworkVersion.

* Fix parameter

* DevDivInsertion better error message

* Remove 'win' from target string

* Fix dir name

* Install Setup.Dependencies

* Default values for insertion components

* Make BuildBoss happy

* Fix VSIX path

* NGEN binaries that should have been NGEN'd

* RoboCopy returns non-zero exit code on success

* Pass OfficialBuild property to vsmanproj

Closes #29746

fix publish assets to publish channels

Upgrade to .NET Core SDK version 2.1.401

The cause of the CoreClr crash appears to be VB expression trees. I've
disabled all of the relevant tests util we can get a fix from the
CoreClr team.

I'm as confident as can be that this will be stable. I ran the test 100
times in a loop locally and got no failures. If more popup I'll dig
further

CoreClr tracking bug: https://github.com/dotnet/coreclr/issues/19862

Fix Tuple Crefs causing null exception:
  - fix the Cref binder so that we un-wrap any TupleTypeSymbols that get wrapped inside BindNamespaceOrTypeSymbol as crefs don't consider the higher order form tuples at all.
- Add tests

* Document #6941
Also delete meeting notes that have already been moved to an appropriate repo.

Queue tasks rather than invoking them inline

YAML file for Azure Dev Ops validation

Fix tests.sh so you can run a single assembly, add support for running a single test

Fix tests.sh support for running a single assembly and add argument passthrough so you can run a single test