Bug #5052 describes how large resources compiled into assemblies
compiled using csc running on CoreCLR on Linux can become corrupted in
the metadata. The cause of this is the BlobBuilder in PEWriting
discarding the output of FileStream.Read, which indicates whether or not
further calls to Read are necessary to read the entirety of the stream.

This change adds an extension method ReadAll to Stream that checks the
output of Read and continues calling Read until all the requested data
has been returned. BlobBuilder is altered to use this new extension
method, but there are other unfixed callsites in Roslyn that make the
same mistake that will also have to be fixed up. This change also adds a
regression test for this scenario.

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).

1) Reduce number allocations in the analyzer driver that show up perf traces for Picasso.
2) Currently we maintain a cache of CompilationWithAnalyzers for projects being actively analyzed. This is causing the VM to rise and also forcing GC to kick in at different phases causing regressions at various scenarios. The fix is to just create a new CompilationCompilationWithAnalyzers instance for each document/project analysis request.

Report a diagnostic if an analyzer reports a diagnostic with an invalid ID (has non-alphanumeric characters).

This change does two actions to our public API files:

- Resets them to the versions from 1.0.0 RTM
- Splits them into the shipped and unshipped files

On CoreCLR we will always be unable to fetch the default encoding and
the 1252 encoding will be unavailable unless we reference
System.Text.Encoding.CodePages. However, we don't want to take a
dependency on this assembly on desktop 4.5 so we now use
AssemblyLoadContext to try to detect whether or not we are running on
CoreCLR and, if so, reflection load the necessary assemblies to get hold
of the necessary types.

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.

Plumb the features flag through our MSBuild and Workspaces layers.

closes #3879

The targets files were previously split into an open version in
Microsoft.CodeAnalysis.Toolset.Open and a closed version in build/. This
unifies the four targets into two new targets, VSL.Settings.targets and
VSL.Imports.targets, and moves all the targets from ..Toolset.Open into
the build/ folder.

This reverts commit 338dd021.

Centralized some of our scattered uses of reflection to PortableShim.
While moving I verified all of the APIs are a part of the CoreFX +
Portable plan.

This removes the majority of references to the deprecated Desktop
assemblies.  The only remaining ones are in the VSIX projects.  They
must remain until we actually delete the assemblies.

This moves the contents of the CSharp and Visual Basic Desktop
Projects to the Portable counterparts.

closes #2587

Add a utility method to find assembly dependencies.

Given a path to an assembly, `AssemblyUtilities.FindAssemblySet`
identifies file in the same directory that could satisfy the assembly's
dependencies.

This commit contains just the code itself and some unit tests. A later
commit will wire it into the compilers/VS.