...to Roslyn.VisualStudio.Setup.vsix

This is the default if you build with Update 1, but not if you're still
on the original released version.

We use the shipping flag to control VSIX signing, and we want this to
be signed.

Fixes GitHub issue #6803.

The official build flag specifies which assembly version is baked into
Roslyn. This was being used in various ways to either include or not
include binding redirects, but we now always want binding redirects.
Also, we were passing the flag along to the compiler to figure out
which NewVersion to bake into the redirects, but setting nothing
at all conveniently does exactly what we want.

We sometimes need an .exe and sometimes need a .dll, so let's just
make it explicit. We can still get the assembly name either way.

Otherwise, the interactive window won't be able to find the language
services DLLs.

This more or less matches what our NuGet files write out, although
we split it into two separate files to ensure we override what we want
right away, but allow the project file to control whether we use the
compiler server.

- rename it to Roslyn.Compilers.Extension so it's clearer what it is
- remove the old specification of binding redirects. Now that Update 1
  provides us with the ability to patch the language services with
  a proper VSIX, we don't need to redirect anything other than the build
  task anymore.
- update the set of deployed binaries to the current compiler set
- clean up package code and registration

This causes us to generate our binding redirects we need to support
experimental extensions.

In Update 1, devenv.exe.config specifies the binding redirects for
the Roslyn assemblies, in addition to us specifying them in the pkgdef.
If you're building an experimental VSIX, we need to specify a temporary
flag which will enable the shell to ignore the other redirects in
the .exe.config in favor of our pkgdef ones.

Revert "Syntactically classify buffers without a workspace"

This reverts commit c25f2528.

[AskMode] Fix issue with #load of files that can't be read as text...

(fixes #6589)

If a #load'ed file can be resolved, but cannot be read (or cannot be read
as text), it doesn't get added to the map of resolved file paths ->
SyntaxTrees (because there is no SyntaxTree to add).  This wasn't handled
in the remove and replace helpers that rebuild the various syntax maps.
In addition, we were attempting to add #load'ed trees to the ordinal map
twice in the case that their ordinal position needed to be shifted after
a remove or replace.

Fix DSR.N version in VSL.Settings.targets

Update DSR.Native to 1.3.3

disable incorrect tests

Microsoft.DiaSymReader.Native package fixes

Syntactically classify buffers without a workspace

csi: Update ScriptOptions with the latest values of current dir, search paths

When a project or document is removed/closed, clear out all the squiggles we currently have for them.

Inherit references from previous submissions

Don't generate a binding redirect for Microsoft.Build.Tasks.CodeAnalysis

Hopefully, this will fix internal bug 157535.

Fixes #873

Sometimes there are buffers with our C#/VB content types that are not added to the Running Document Table and therefore never end up in the MiscellaneousFilesWorkspace (or any workspace), such as the Source Control "Annotate" view. This change updates the Syntactic Classifier to handle such cases by parsing its initial snapshot for tagging (changes are not observed, but the known use cases of this fix are uneditable anyway).  There are some exceptions to this behavior (e.g. the Immediate window) which require us to go digging through attached views, but we default to classifying these buffers now.