Remove all fields from SourceOrdinaryMethodSymbol in the common case. (…

…#68135)

* Use a singleton for empty type-parameters for named types

* move type parameters down

* Optimize methods as well

* Always create indirection

* In progresS

* Utilize

* initialize once

* In progresS

* Utilize

* initialize once

* Save space in other methods

* Move type

* reorder

* reorder

* Move down

* Reorder

* Simplify

* Make private

* lint

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberMethodSymbol.cs

* Apply suggestions from code review

* Add docs

* Move

* Make sealed

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

* Make abstract

* Better

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

* Add comment

* Rename

* move

* Cleanup

* Comment

* MOve check

* Add back optimization

* use IsAssignableFrom

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

Co-authored-by: Fred Silberberg <fred@silberberg.xyz>

* Update src/Compilers/CSharp/Portable/Symbols/Source/SourceOrdinaryMethodSymbol.cs

Co-authored-by: Fred Silberberg <fred@silberberg.xyz>

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Co-authored-by: Fred Silberberg <fred@silberberg.xyz>