Big interpreter rewrite

[StachuDotNet]

Rewriting RuntimeTypes, the Interpreter, and PT2RT to:

• be generally faster
• not stack-overflow so trivially (#5222)
• handle async and parallel processing seriously

Here are all of the wins (WIP):

• much better, structured RTEs
  • OldStringErrorTODO is gone
• better handling of RTEs, generally
  • especially dev experience (understanding what went wrong)
• async, concurrent function calls
• no easy-to-reach stack-overflows
• more tests
• super-fast builtins (without copying Dvals all over the place)
• non-recursive runtime type-checking is now complete and I can close #5071 #5030
• everything's faster
  • hopefully fast enough for 95% of programming tasks
• partial-application works, for "applys" to both fns and lambdas
• I might add some other tiny language features? lol
• interpreter is easier to understand
• there might end up actually being a net negative in terms of LOC at the end of this?
• we're a tiny bit closer to getting tracing working in this new world
• I have some ideas on further worthwhile optimizations (will hand off to Ocean)

I might get stuck on SqlCompiler and circle back to that in another PR - not sure yet.

It'll probably be another 2 weeks until this gets merged.

This closes #5222, closes #5130, closes #5071

[StachuDotNet]

thoughts on implemented match that I wanted to record in case my current plan doesn't end up working out: https://gist.github.com/StachuDotNet/5a8923721b255ad2a91c1c6dcc3e9b8e

Edit: it worked out (really well!) but might as well keep this around.