stdlib: Significantly refactor the Runner api

[V-FEXrt]

I'll edit this later with a longer description but wanted to kick of ci.

tl;dr:

• breaking change
• score is gone
• makeRunner -> depreMakeRunner
• new makeRunner takes a single run function instead of two split functions with convoluted apis

[ag-eitilt]

Assuming CI and general integration are happy, I greatly prefer this architecture. Everything looks good at a first pass, but there's enough moved blocks of code that I'm going to have to use other methods of reading the diff to fully see what it's changed (the by-commit reading you mentioned, undoing indentation changes for better diffs, ...) so I don't want to click approve immediately -- let me know if you want to get this in sooner than I get around to looking at it at that level of detail, I don't expect to find anything unpleasantly surprising.

[ag-eitilt]

Yeah, that all looks good even after a deeper readthrough.

[colinschmidt]

Looks like a clean refactor to me. All the runners look simpler and we can finally drop the score tech debt.

A couple of non-blocking comments/questions and things that we should keep in mind as we continue some of this refactor work.