Use ParamSpec for wrapped signatures

[Dreamsorcerer]

Fixes #504.

There are still a couple of issues with this.

1. Typing doesn't seem to work correctly with instance methods. Not sure exactly what is going wrong here, needs some more investigation.
2. partial() use will cause new type errors. We can either wait until partial() is properly supported by typedshed/mypy (functools.partial should use PEP612 ParamSpec (depends on #8708) python/typeshed#8703 / functools.partial support python/mypy#1484), or we could expose a TypeAlias of _LRUCacheWrapper so it can be used in type annotations.
3. There also seems to be an issue with pypy, possibly a bug in pypy, but needs further investigation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.92%. Comparing base (f60bf71) to head (0e56d88).
Report is 52 commits behind head on master.

❗ Current head 0e56d88 differs from pull request most recent head c8156f9

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #508      +/-   ##
==========================================
+ Coverage   96.88%   96.92%   +0.03%     
==========================================
  Files          12       12              
  Lines         770      780      +10     
  Branches       91       93       +2     
==========================================
+ Hits          746      756      +10     
  Misses         22       22              
  Partials        2        2              

Flag	Coverage Δ
unit	96.53% <91.66%> (-0.22%)	⬇️

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[asvetlov]

Good step forward, thanks!

[asvetlov]

Do you have a reason for enumerating all mypy options?
I would prefer strict = true plus maybe a few additional fine-tunes.
Maintaining all mypy opts adds a burden; I never could keep all these options in my mind without looking in docs

[Dreamsorcerer]

This adds a lot more options than strict. This is the config we started in aiohttp a few years ago. Basically, strict isn't so strict, so we like to enable all the options that aren't too much.

At some point I'd like to find a way to make a config that's reusable across all projects without copy/paste, which will ease the maintenance burden.