Now that feature names aren't used for serialization anymore, we can
just get rid of the constants and use the containing type name.
Also, update more options to use nameof where appropriate.

Now that our existing options have been tagged with the appropriate
metadata, we can use that metadata to drive serialization. This
updates IOptionSerializers to make them no longer have any language-
specific metadata, and are simply driven from the metadata included
on the option.

This also renames IOptionSerializer to IOptionPersister, which is
a better name.

Now that we have an API for associating persistence information,
we can put that information on all our options we persist today.
We'll consume this in a future commit.

One current challenge of our option persistence story is the
determination of the name of an option being serialized is mixed in
with the core logic for how to serialize things to a store. This results
in some very hard-to-maintain code since the logic for an option
is spread across many different areas.

Since we only apply the options that finally changed, this behavior
should be redundant, but requires us to categorize options in a not-
obvious way.

Merge future to master

Only declare Hidden Descriptors for SimplifyTypeName/QualifyMemberAccess

* Enable declaration patterns in the EE

Fixes #13159 

Properly handle expression variable declared within VariableDeclaratorSyntax.ArgumentList in field declarations.

Re-add property that internal CodeLens implementation depends on

Contains the Roslyn compiler build tasks and targets files.

Fixes #9640.

Fixes #12714

SimplifyTypeName, QualifyMemberAccess, and
CSharpUse[Implicit/Explicit]TypeDiagnosticAnalyzer were declaring one
DiagnosticDescriptor per DiagnosticSeverity level in SupportedDiagnostics.
After this change, they only initially report a DiagnosticSeverity.Hidden
descriptor, which prevents them from running on closed files.

There are longer-term plans to allow these to run on closed files but
under closer control of the user.

Display non-default Tuple names in EE

Consume [TupleElementNames] metadata in the EE ResultProvider and include element names in display strings.

Put in accessor accessibility modifiers when symbol display is asked to show read/write info for properties

Fixes https://github.com/dotnet/roslyn/issues/11016

Use appropriate telemetry key.

Reduce the number of objects allocated for SymbolTreeInfo.

Stop using UseCodebase for our product VSIXes

handle null argument list on invocation expression

Export persistence service at appropriate layer.

Now that we specify codebase attributes in our binding redirections,
we don't need this anymore. This allows ngen to work in more scenarios
since it resumes loading our packages in a Load context.

I leave our diagnostics window VSIX as is, since that's a debugging tool
and it's less to maintain by keeping it that way.

Fixes #13383

Make "async returns" be attribute-based off [AsyncBuilder] attribute,
no longer off CreateAsyncMethodBuilder method.

Fixes #13607.

Move Esent support down to Workspaces.Desktop.  This way we use it from RemoteWorkspace

Still try to select good items, even when backspacing in completion.

Fixes #13481

removed reflection and use new public API from metadata reference

Consume ServiceHub env vars for appBasePath and app.config...