[Feature] In-process diagnosers

[timcassell]

• Adds a new feature for diagnosers to run in the benchmark process via IInProcessDiagnoser interface.
• DisassemblyDiagnoser is the first in-process diagnoser (with the option to run in host for back-compat).
• Fixes test-windows-full CI job failed on disassemble tests for x86 #2789
• Fixes Cross platform disassembler doensn't output anything on macOS #1499
• Fixes in-process disassembly on Linux.
• Removes bifurcation of embedded x86/x64 disassemblers (easier to maintain and smaller package size).
• Makes it trivial to extend disassembly support to more platforms (e.g. arm32).

[timcassell]

It works nicely, but I'm not entirely sold on this design of diagnosers creating source code tied to C#. An alternative is serializing ctor data. I would love to use static interface members for this, but sadly they aren't supported on netstandard2.0. 😞 @AndreyAkinshin Any thoughts?

[AndreyAkinshin]

@adamsitnik could you please take a look?

[timcassell]

I changed it so diagnosers return Type and serialized config instead of source code. I think source code generation should be left to the toolchains.