PYTHON-5544 Revert changes to base protocol layer

[blink1073]

Reverts PYTHON-5543 and PYTHON-5215

I made a few hand-edits afterward that were typing-only to accommodate conflicts from #2524

[blink1073]

I reverted the changelog changes so this will cleanly backport, I'll handle the changelog and version update in a separate PR.

[blink1073]

drivers-pr-bot please backport to v4.15

[mongodb-dbx-release-bot]

Sorry, unable to cherry-pick to v4.15, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout -b cherry-pick-v4.15-7a07c0281457f16fe807e4e65ef0c13f7b1deb2f v4.15

git fetch origin 7a07c0281457f16fe807e4e65ef0c13f7b1deb2f

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 7a07c0281457f16fe807e4e65ef0c13f7b1deb2f

3. You will likely have some merge/cherry-pick conflicts here, fix them and commit:

git commit -am {message}

4. Push to a named branch:

git push origin cherry-pick-v4.15-7a07c0281457f16fe807e4e65ef0c13f7b1deb2f

5. Create a PR against branch v4.15. I would have named this PR:

"PYTHON-5544 Revert changes to base protocol layer (#2535) [v4.15]"

[blink1073]

so much for that idea...