Add parameter CodefixProvider: Fix argument list handling of local functions 

Fix #29390, add space after tuple type and identifier

Enable C# emit tests for Mono

Merged on behalf of @alrz

Looks like we have a threading issue in the parser. Filed a bug to track
this down.

https://github.com/dotnet/roslyn/issues/30212

Enable hard links as a build option

add SyntaxFactory.ParseDeclaration

* Fix TypeParamRefs in included xml docs in C# not resolving correctly:
 - When resolving TypeParamRefs in an included xml comment in c#, ensure we add any parent generic types to the binder we create
 - Add a repro test (essentially a copy of the VB test Include_TypeParamAndTypeParamRefHandling)

* Implement ValEscape rules for ?? operator:
- Implement GetValEscape/CheckValEscape for the null coalescing operator
- Fixes using a coalescing operator in a return statment causeing an emit failure
- Fixes a valid no escaping coalesce assignment being marked as exposing
- Add tests for cases that were failing before
- Add test for case that should still be invalid

Originally I thought this function could be ported to be portable. Under
the hood it relies on `SoapHexBinary` which is desktop only. Hence this
does need to be a desktop only test.

The use of `Assert.True` is problematic here as it's throwing an xunit
defined exception. In this case `TrueException`. This is problematic
because it's not serializable yet it is callable from within our
isolated test `AppDomain` instances.

In this case we should just be throwing an exception directly here.

Handle mixed initializer style with initblk

The general pattern when registering code fixes seems to be
either passing diagnostics[0] or diagnostics.First().

RemoveUnusedVariable seems to be the only outlier in this case,
doing .Single().

Having multiple diagnostics on a span would cause the code fix
to throw an exception

Fixes #367

Correct unix first time build instructions

closes 30139

I spent a full day trying to track down why the wrong code was being
generated for this file and why the generator wasn't running.

Fixes #29368

Fix C# semantic tests for Mono execution

This makes the necessary changes to the C# semantic tests so that they
can be executed under Mono.

This does **not** enable C# semantic in our Mono CI. I will be doing
that as a separate PR after some extended validation completes. The
reason for committing this now is having our repository in a state where
the tests just works make it easier for Mono to validate fixes.

Fix spanish job

This adds a new option to our build to enable hard links:
`$(ROSLYNUSEHARDLINKS)`. This is done as a separate option versus just
letting interested parties use the four separate MSBuild properties for
the following reasons:

1. It's not really reasonable to have developers remember and always use
the four separate properties.
1. Having a separate name means you can specify this as global
environment variable and have it impact all Roslyn builds, including
from VS, without having it be used on builds that may not be safe for
hard links.

This option does produce measurable effects on builds:

| | Build Time | Binaries Size Explorer | Binaries Size DU |
|-|-|-|-|
| No hard link | 4:00 | 13.9GB | 14.9GB |
| Hard links | 3:28 | 13.8GB | 1.5GB |

Even so this is not being enabled by default due to fears of developers
inadverently corrupting the NuGet cache when directly writing to the
Binaries directory. The build itself is safe to use with hard links (our
correctness job validates we don't double write any output). Hence
normal use can use this option safely.

closes #3005

Remove redundant Jenkins jobs

Add feature to suggest converting code to use compound assignment.

Fix problem to rename Attribute

This removes all of the Jenkins jobs that are redundant with our Azure
DevOps jobs.