Fix GetDiagnostics(span) to return all diagnostics intersecting the span, rather than just the diagnostics contained within the span.

Fixes #3892 and #4559

Add a new CompilationOption "ReportSuppressedDiagnostics" to enable reporting compiler diagnostics suppressed in source. Note that the command line compilers will report such suppressed diagnostics in the SARIF errorlog file but not on the console output.

This new compilation option was approved by the design team.

Fixes #5216

Emit "isSuppressedInSource" boolean property for diagnostics in the ErrorLog file and report suppressed analyzer diagnostics in the error log.

1. CompilationWithAnalyzers can now report analyzer diagnostics with source suppressions (pragma/SuppressMessageAttribute). This will eventually allow us to surface diagnostics with source suppressions in the error list. Note that the behavior of command line compilers and all the GetDiagnostics APIs is unchanged, only the compiler analyzer will report diagnostics with source suppressions.

2. Add FixAll support for Suppression code fixes. Light bulb suppression fixes now show the "Fix all occurrences" options for Document/Project/Solution. This change adds the basic functionality to bulk suppress diagnostics. This will eventually be consumed for baselining all/selected diagnostics from error list/solution explorer.

3. Simplify the Suppression light bulb menu to remove the option to add a local SuppressMessageAttribute. The only options now are to suppress in source (pragma) or suppressions file (assembly level SuppressMessageAttribute).

Fixes #4924.

Changes include:

1. Enhance CompilationWithAnalyzers to allow computing analyzer diagnostics for a specific tree/span within a compilation and/or for a subset of analyzers. Implementation ensures no duplicate analysis by tracking partial analysis state and caching the reported analyzer diagnostics.

2. Overview of the new APIs added to CompilationWithAnalyzers:
    1. GetAnalyzerSyntaxDiagnostics(tree, analyzers, ct)
        1. Analogous to SyntaxTree.GetDiagnostics(ct)
        2. Gets analyzer diagnostics reported by executing syntax tree actions on the given tree.
    2. GetAnalyzerSemanticDiagnostics(semanticModel, spanOpt, analyzers, ct)
        1. Analogous to SemanticModel.GetDiagnostics(spanOpt, ct)
        2. Gets analyzer diagnostics reported by executing rest of the non-compilation actions on the given tree span.
    3. GetAnalyzerCompilationDiagnostics(analyzers, ct)
        1. Gets rest of the analyzer diagnostics which are reported by either of the following means:
            1. Compilation actions (and compilation end actions)
            2. Non-compilation actions reporting diagnostics on different tree: Executing a symbol action on a symbol definition in a tree, can report diagnostic on its partial definition in some other tree.

3. Simplify IDE analyzer driver by switching it to using the new CompilationWithAnalyzers APIs for analyzer diagnostic computation. Both the IDE and compiler drivers now use the compilation event queue model for driving analysis.

...as AddSyntaxTrees does.

As an optimization, submissions not containing declarations are not
emitted.  However, when we short-circuit emission, we also skip diagnostic
reporting (e.g. in usings) that can trigger an assert in the next
submission (which assumes that all errors have been reported).

Fixes #3795

This reverts commit 15443a23.

Conflicts:
	src/Compilers/CSharp/Portable/CommandLine/CommandLineParser.cs
	src/Compilers/CSharp/Portable/PublicAPI.txt
	src/Compilers/Core/Portable/PublicAPI.txt
	src/Compilers/VisualBasic/Portable/CommandLine/CommandLineParser.vb

Fixes #2888
Fixes #3786

Add DiagnosticDescriptor.GetEffectiveSeverity(CompilationOptions) API to get the effective severity of diagnostics created based on the descriptor for the given compilation options.

This change also removes the clone of this functionality in the IDE layer used by the solution explorer rule severity display and error list/diagnostic service. It now uses this public API.

Fixes #2598

Fixes #1958
Closes #1967 (a good year)

In some scenarios, an attribute application can be “bad” due to an error type in referenced compilation, but without any diagnostics reported for the referencing compilation.

This is the initial run of the code formatter on the VB compiler source code.  Further runs I'll expand on this to include all VB code in a future run.

Fixes #1028
Closes #1116

Enable hosts to compile strong-named assemblies on all platforms by supplying public key via compilation options and also enable OSS signing with such key

The expression compiler returns information to the debugger in the form
of .NET assemblies.  These assemblies should not contain embedded
declarations (i.e. "My.*").  At best, these declarations are useless.  At
worst, they hide the declarations in the user's own assembly.

As a bonus, this fixes an issue we were having with being unable to
compile the embedded declarations in cases where two copies of
EditorBrowsableAttribute were loaded (since neither is "closer" or more
accessible while debugging).

Fixes #946.

Calling GetSemanticModel with suppressAccessChecks=true creates a SemanticModel that ignores accessibility rules when answering semantic questions.
This allows consumers to ask semantic questions using the same semantic rules as the ones used in debugger’s Expression Evaluator, where accessibility rules do not matter.

Added unit tests for C# and VB.NET to cover both regular and speculative analysis.

It ensures the following for the lifetime of analyzer host:
1) DiagnosticAnalyzer.Initialize(AnalysisContext) is invoked only once per-analyzer.
2) DiagnosticAnalyzer.SupportedDiagnostics is invoked only once per-analyzer.
3) CompilationStartAnalyzerActions registered during Initialize are invoked only once per-analyzer per-compilation.