Reverting System.Collections.Immutable back to 1.1.36 until we can upgrade System.Reflection.Metadata simultaneously

Updating Microsoft.DiaSymReader to v1.0.6, Microsoft.DiaSymReader.Native to v1.2.0, and System.Collections.Immutable to v1.1.37

Fixes #5631.

Gracefully handle format exception from Diagnostic.GetMessage() when the analyzer reports a diagnostic with incorrect format arguments.

Fixes #4589

1. Fixes #5463: VB field and property declarations don't include the "AsClauseSyntax" node in the node's "Initializer" field, which caused us to miss executing the syntax node actions for AsNewClauseSyntax nodes within code blocks. Now we explicitly account for these initializer nodes.

2. Fixes #4745: C# namespace symbols defined by a qualified name such as "X.Y.Z" within "namespace X.Y.Z {}", all have the same declaring syntax reference. So we need to ensure that we don't make duplicate syntax node callbacks for such namespace declaration nodes.

Avoid rebinding references bound to explicitly specified definitions, even if a better version is available after resolution

Disabling flaky tests from http://dotnet-ci.cloudapp.net/job/roslyn-internal_master_win_rel_unit32/7/

Fixes #5516

Fixes #5395.

Adjusted Binder, Optimizer, Flow Analysis, code generator and majority of bound tree visitors to not use recursion to handle binary expressions nested on the left side of another binary expression.
Adjusted majority of bound tree visitors to detect that stack overflow is about to happen while an expression is being traversed and report a diagnostic pointing to the expression at fault instead of crashing compiler.

(fixes DevDiv 790235)

Naming the execution scripts 'csc.sh' and 'vbc.sh' is counter to the
convention of not using any extension on *nix executables. While the
scripts are not strictly executable programs, they are meant to be
transparent shims around the actual execution of the compilers on *nix

Added new tests for the ReleaseDebug mode. not changing baselines though to see the diffs in the next commit

After updating to the latest CoreCLR NuGet packages we no longer need to
be copying binaries from a drop share to run. This change adds a csc.sh
and a vbc.sh so we can run on the CoreRun host on Linux like we do on
Windows. The change also eliminates some cruft from the cibuild like the
semaphore restore.

A process in Windows is provided arguments as a flat string yet main methods in applications receive arguments as an arary of string values.  The transition between the flat string and array is done automatically by the runtime in two phases:

- Break into arguments based on spaces and grouping quotes.
- Remove extraneous quotes and backslashes.

Doing both operations at the same time serves to remove separators that are significant to the compilers.  For example:

1. /r:"a.dll,b.dll"
2. /r:a.dll,b.dll

In the main method both of these argument strings will show up as the latter value (the quotes are considered extraneous by the runtime).  Yet these represent very different values to the compiler:

1. Reference a single file named "a.dll,b.dll"
2. Reference two files named a.dll and b.dll respectively

This change restores the native compiler behavior by manually parsing out the flat argument string.  All of the parsing methods were taken directly from the old compiler.

There are a few small changes of note here:

1. VB now considers semicolon to be a list separator as it does comma (unifies behavior between languages and other tools).
2. VB and C# now have unified behavior for collapsing backslash characters.
3. Fixed several unit tests which were validating incorrect behavior.

closes #4021

Adds a new type, CoreClrAnalyzerAssemblyLoader, that is responsible
for finding and loading analyzer assemblies on CoreCLR. This is used
in the CscCore and VbcCore CoreCLR-targeting projects.