Remove a bunch of unused/vestigial code

[akx]

As found by Vulture and some eyes.

These things don't seem to be referenced anymore.

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests

[AUTOMATIC1111]

It would be preferable if some person with a lot extensions tested this before it's merged.

[w-e-w]

instead of outright removing stuff we should use @deprecated
https://pypi.org/project/Deprecated/
you never know what extensions would do

[akx]

@w-e-w Maybe, but I'd also rather not add an extra dependency. (I cleaned deprecated out of Redis earlier: redis/redis-py#2386)

[w-e-w]

sure
I just use the package because it is well known, no need to explain any concept