(regression)

This will improve import performance a bit (especially under importlib).

Patch by Catalin Iacob.

Issue #14043: Speed up importlib's _FileFinder by at least 8x, and add a new importlib.invalidate_caches() function.

importlib is now often faster than imp.find_module() at finding modules.

Also wrap two looong lines.

Closes issue #14054.