Make independent owners requests per file to improve memoization

[stuhood]

Problem

#10441 caused a performance regression from about 10s to run ./pants dependencies --transitive :: with inference enabled, to about 22s.

Solution

Make independent owners requests per file we'd like to find owners, which allows the lookups for each file to be memoized independently.

Result

./pants dependencies --transitive :: takes 15s. Although we are doing more work than before (before #10441, conftest discovery would only happen at test time), this is not ideal, and we should do further optimization before launch. But there are a few variables that will impact this soon that make it not the best time to optimize: 1) an intrinisic PathGlobs->Paths operation, 2) possibly enabling inference by default, allowing all of the strategies to use the module_mapper.

[ci skip-rust-tests]

[Eric-Arellano]

Thanks. How would you feel about instead using the map already created for import inference? If you do that, what's the result time?

I suspect we'll want to use that map so that we avoid any unnecessary work, and so that there isn't a performance consideration on whether you want import inference or not. The decision to use import inference would only be if you like the behavior or not.

[stuhood]

@Eric-Arellano : I mentioned it in the Result section: it felt like it would be a good idea to tie using that map to inference being enabled by default. Because with no import inference, __init__.py and conftest.py will still be lazily discovered, unlike with import inference, which needs to scan the world. Once that is enabled by default it will be an easier decision, and one optimization path.