Related to #22548 and #22229.

* Rename Foo to Goo

* Rename ifoo to igoo

* Add back BOMs

* Parse ref/readonly-ref extension methods

* Address PR Comments

* Fix break

* More PR Comments

* Fix break

For IOperation purposes

Conflicts:
	src/Compilers/CSharp/Test/Semantic/Semantics/OutVarTests.cs

Conflicts:
	src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs
	src/Compilers/CSharp/Portable/Binder/Binder_Query.cs
	src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs
	src/Compilers/CSharp/Portable/Errors/ErrorCode.cs

* Combine deconstruction assignment and declaration, and support discards.

- Combine deconstruction assignment and declaration, and support discards.
- Add wildcards.work.md to track outstanding work.
- Bind each type syntax once in a deconstruction.
- Because tuples may contain declarations, adjust lambda disambiguation
  and adjust parsing of argument lists.
- Diagnose tuple element names on the left of a deconstruction.
- Add relational operators to disambiguating tokens in 7.5.4.2

* Disallow deconstruction declarations except at the statement level.
This is now a semantic restriction (until we decide to remove it).

* Revise logic to detect `var` in a declaration expression.
Plus other changes per code review.

* Add a test that GetTypeInfo on a discard expression doesn't crash.
* Small changes per code review.
* Add (skipped) test for var invocation in parens.
* Rename "Discarded" to "Discard"
* Changes recommended via code review.
* Minor changes to the handling of declaration expressions per code review.
* Addressing blocking feedback while Neal is OOF

Fixes https://github.com/dotnet/roslyn/issues/14794
Fixes https://github.com/dotnet/roslyn/issues/14832

Fixes #7895

Fixes #14825

Fixes #13450.
Fixes #13590.

We attempt to bind lambda args against every applicable delegate
type that could be a matching parameter, and then select the
"best" for error recovery.
This also has the effect of removing unbound lambdas from the
bound trees, replacing them with the "best" binding for error
recovery. This makes the semantic model insensitive to any further
trial bindings (i.e. mutation of the unbound lambda cache).
Fixes #12063, #11979, #11901

Remove vestigal "extensionMethodsOfSameViabilityAreAvailable"
thereby reducing coupling between internal compiler APIs.
See also #7740 #5128, where the vestigal APIs were introduced.

Fixes some of the scenarios for https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?id=204561&_a=edit.

Also addressed feeback provided for the previous change.

Generalize dynamic static-only restriction to include field initializers (was just ctor initializers)

It looks like OverloadResolutionResult didn't guarantee that
the result was available unless .Succeeded was called. This
ensures the result is always loaded before returning anything
related to the result.