Split ISyntaxFactsService into two parts:

1. `ISyntaxFacts`: Pure data interface to query about syntactic facts. This is moved to CompilerExtensions shared project and can be used by analyzers.

2. `ISyntaxFactsService`: Derives from ISyntaxFacts and ILanguageService and is present in the WorkspaceExtensions shared project. This enables Code fixes and Workspaces layer to access the same functionality via a language service, i.e. `GetLanguageService<ISyntaxFactsService>`.

Note that we cannot use a partial declaration for `ISyntaxFactsService` instead of `ISyntaxFacts`. This causes `ISyntaxFacts` to be defined in both the CodeStyle analyzer and CodeStyle fixer assembly (former imports CompilerExtensions and latter imports WorkspaceExtensions), which leads to type conflicts. We also cannot follow the approach taken for `ISyntaxKindsSevice` as it defines the second partial declaration `ISyntaxKindsSevice` which sub-types `ILanguageService` in Workspaces project, leading to the language service not being defined in CodeStyle fixer assembly, which will cause any code fix requesting `GetLanguageService<ISyntaxKindsService>` to fail. The only feasible approach for us to have the functionality available in shared analyzer layer is to split out the pure data query part of the service to a separate type, as done in this PR. I will send a follow-up PR to also split `ISyntaxKindsService` similarly. Hoepfully, these two are the only language services that are commonly used by our analyzers, and we will not require any more such splits.

Extracts out the changes to core Workspace changes from https://github.com/dotnet/roslyn/pull/41363.

* Fixes #33601

* Respond to feedback

* Restrict to only trigger if identifier is in selection

* Respond to feedback

* respond to feedback

* Respond to feeback

The bug was that automatic brace completion will not overtype close
parenthesis if the close parenthesis token was preceded by a numeric
literal. The bug was in `IsEntirelyWithinStringOrCharOrNumericLiteral`,
where we were imposing checks meant for chars and strings on numeric
literals, which was likely introduced in PR #1763. This change addresses
it by not enforcing checks meant for chars/strings on numeric literals.

With ICompilationUnitSyntax and ISkippedTokensTriviaSyntax in place, these helpers no longer need to diverge per language and can be written in a language-neutral fashion.

Improves comments around the IsCompleteSubmission.
Throws argument exception when the syntax is not a submission.
Uses the Parser.CheckFeatureAvailability to check multiline strings.
Renames the IsScriptOrInteractive to IsScript.
Handle incomplete members such as an annotation.
Do not show completions when inside of a directive.
Add tests for symbol completion provider.

Implemented @MattWar suggestion of removing unecessary allocation, by using two separate iterations.

Removes recursion from the function.

When typing a global statement all existing symbols will be added to auto completions.

Or, in VB, date literals

Now that the comment formatting issue is fixed in the Formatter type, we can run the formatter on the remainder of the VB code base.

closes #1424

Fix #409:
Add explicit StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase where it was intended,
or replace single-char string literals with chars literals.
Also, provide InvariantCulture in TryParse where it was intended.

Renames various "Begin" and "End" property names in Syntax API to match the rest of the API with block specific names like "CaseStatement" "EndClassStatement" etc (changeset 1400806)

Marks CSharpKind and VBKind extension methods as Obsolete and adds equivalent extension methods Kind for both languages.
Marks CSharpKind and VBKind instance methods on language specific syntax nodes Obsolete as well.
 (changeset 1389494)

Marks CSharpKind and VBKind extension methods as Obsolete and adds equivalent extension methods Kind for both languages.
Marks CSharpKind and VBKind instance methods on language specific syntax nodes Obsolete as well. (changeset 1388816)

A boolean condition seems to have been inadvertantly flipped in CS 1317861 (portable workspace) which caused brace completion to not work after string literals. Fixing the conditional and enabling an unit test. (changeset 1357958)

This change splits the Workspaces layer into two parts, mirroring the Portable/Desktop split that the compilers did. The core parts of the Workspaces layer (managing documents and projects, formatting, some refactoring, code fixes) is kept in the portable subset, with a few non-portable pieces remaining, notably MSBuild support.

This change has a major impact on how MEF now works in Roslyn. Traditional MEF (“MEFv1”) is not portable, and so we must move the Workspaces layer over to using the Microsoft.Composition NuGet package (“MEFv2”) which is. The APIs are distinct in that each has its own namespace, but the concepts are more or less identical. It requires some care though: the workspaces layer is simple in that it only references MEFv2, but higher layers have to reference both versions to use metadata attributes. Exports using metadata attributes from the editor (say, ContentTypeAttribute) must use MEFv1 attributes to export, whereas exports for the workspaces layer must use MEFv2 attributes. The rule is subtle and yet simple, and so a diagnostic is provided which catches any offenses to prevent confusion.

This also has some impact in how we create MEF hosts: if you wish to host just the base workspaces layer, we can use MEFv2 to compose everything. The HostServices implementation (MefV1HostServices) that consumes a MEFv1 ExportProvider. If you’re in Visual Studio, you can use this implementation to get the full set of host services provided in Visual Studio.

Otherwise, most of the changes in here are minor: we react to some APIs that have been moved/renamed in the portable subset we are targeting, and also align our various exception helper utilities with the compiler’s precedent. (changeset 1349276)

Abbreviates the public VB-specific types (e.g. VisualBasicSyntaxTree -> VBSyntaxTree) in accordance with the .NET Class Library Guidelines to avoid overly lengthy names and consistent with the conventions used in other APIs (e.g. VB CodeDom). (changeset 1348499)

History: A long long time ago, the MatchesKind* helpers were added for checking the kinds of tokens. There were even two variants: one that would allow it to be called on nothing, and one that didn't. Then, we merged our syntax models and so the public IsKind methods were added. Also, the ones that should have thrown didn't, so we had three extension methods that all did the same thing.

This is a silly situation so this change does the following:

1) we use the public IsKind helpers whenever possible
2) we rename the private helpers that allow for multiple types to IsKind so it's consistent
3) we delete SyntaxToken.IsParentKind since you can just write SyntaxToken.Parent.IsKind.
4) we delete other helpers that have no users (changeset 1295518)

Statement completion should not appear inside the bodies of partial method declaration. (changeset 1214704)