Capturing lambdas should be avoided in core compiler code
as they generate excess allocations

Fixes #41054

Avoid expensive captures

* Insert correct `WithNullableContext` binder into the binder chain to ensure speculative models return correct information based on speuclation location.

* Refactor Nullable context options to rely on an enum instead of two bools.
Break out the BuckStopsHereBinder's code to allow sharing.
Fix binder ordering issue for TryGetSpeculativeSemanticModelForMethodBody.

* Make NullableContextState.State a byte for space.

Addresses 3200MB allocations while analyzing Roslyn.sln.

Addresses 950MB allocations while analyzing Roslyn.sln.

Addresses 950MB allocations while analyzing Roslyn.sln.

Addresses 2400MB allocations while analyzing Roslyn.sln.

Annotate SyntaxNodeOrToken

Use master-vs-deps as ibc source branch as there is no VS branch to i…

Addresses 815MB allocations analyzing Roslyn.sln.

Addresses 680MB allocations analyzing Roslyn.sln.

Make AnalyzerActions a value type

Fix VisualBasicSyntaxFactsService.IsLeftSideOfCompoundAssignment

Annotate implementations of IErrorTypeSymbol

Use master-vs-deps as ibc source branch as there is no VS branch to insert into (and therefore the binding redirects have the incorrect roslyn version)

Annotate implementations of IDiscardSymbol

Disable tiered compilation for AnalyzerRunner

* Update dependencies from https://github.com/dotnet/arcade build 20200112.1

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.20062.1

* Update dependencies from https://github.com/dotnet/arcade build 20200113.2

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.20063.2

* Update dependencies from https://github.com/dotnet/arcade build 20200115.5

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.20065.5

Use a non-localized category string for DiagnosticDescriptors

Add records

The `SyntaxNodeOrToken` type had four states:

1. It's a `SyntaxNode`
1. It's a `SyntaxToken`
1. It's `default(SyntaxNodeOrToken)`
1. It returns `true` for `IsNode` but `AsNode` returns `null`

The fourth state appears to be an accident of implementation. This
change removes that state. The one place in the code where this appeared
to be an issue is in the implicit conversion from `SyntaxNode?` to
`SyntaxNodeOrToken`. In all places where this was used and the value was
potentially `null` the caller only used `GetLocation` on the result.
Hence the fix is simply to change that API to return `default` instead
of the fourth state in the case of `null`

Change the text for the newly added background analysis scope option

Don't offer interpolated string refactoring for const variables

Refactor some dispose code in SymbolUsageAnalysis

1. Make the strings sentence cased
2. Rename "Open Documents And Projects" to "Open documents" as per internal review.

This is not a user facing string, so must not be localized. Additionally, with https://github.com/dotnet/roslyn/pull/38886, we now support bulk severity configuration in editorconfig based on diagnostic category, so the string ought to be a non-localized constant without any spaces.

Fix assertion for the bootstrap compiler

Update readme with recent release notes

Deprecate Workspace.set_Options

Extract out simplification changes