Improve import time of various stdlib modules

[hugovk]

Feature or enhancement

Proposal:

Following on from 3.15's #137855, further improvements can be made to import times in 3.16.

And rather than deferring imports, we can use lazy imports.

Linked PRs

• gh-154675: reorganize some imports in importlib #154657
• gh-154675: Improve import performance of tkinter library with lazy imports #148409
• gh-154675: Use lazy imports in pdb, bdb, code #156567