gh-121272: move __future__ import validation from compiler to symtable

[iritkatriel]

• Issue: Move a few bits from compiler to earlier stages to simplify the compiler #121272

[AraHaan]

I agree, this could be a good performance improvement when using a ton of c extensions with python scripts that use import from statements on them.

[iritkatriel]

I agree, this could be a good performance improvement when using a ton of c extensions with python scripts that use import from statements on them.

This shouldn't impact performance.

This is about simplifying code in compile.c (in this case, making compiler_from_import no longer access the internals of struct compiler). This is part of a longer term plan to break up the compiler.

[JelleZijlstra]

Looks good. This is thoroughly tested in test_future_stmt/test_future.py and I confirmed that the code in future.c that sets ff_location makes sense.