refactor: migrate all type annotations to PEP 585

[jansegre]

Refactor all List/Dict/... annotations to use list/dict/... (which don't have to be imported from typing). The complete list of types which now allow for such use of [] is on the PEP 585. This is possible because we dropped support for Python 3.8, we had already started to use it in some new annotations but this PR aims to update all the remaining annotations.

With the changes of this PR following grep should be empty:

rg -w 'typing.* (List|Dict|Tuple|FrozenSet|Type|AbstractSet|Deque|DefaultDict|OrderedDict)' -t py hathor tests

Acceptance Criteria

• Replace all annotations from typing that now can be done on the original class (instead of the typing class) as described by PEP 585;
• Remove all the now unneeded imports;
• Update comments/docstrings that also reference the old patterns;
• Don't change/refactor/improve anything else.

[codecov]

Codecov Report

Merging #654 (dd56e0a) into master (3ced4db) will decrease coverage by 0.05%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##           master     #654      +/-   ##
==========================================
- Coverage   84.08%   84.04%   -0.05%     
==========================================
  Files         245      245              
  Lines       20286    20279       -7     
  Branches     2757     2757              
==========================================
- Hits        17057    17043      -14     
- Misses       2634     2639       +5     
- Partials      595      597       +2     

Impacted Files	Coverage Δ
hathor/conf/settings.py	97.05% <0.00%> (ø)
hathor/wallet/resources/lock.py	100.00% <ø> (ø)
hathor/merged_mining/bitcoin_rpc.py	32.05% <50.00%> (ø)
hathor/mining/ws.py	35.21% <71.42%> (ø)
hathor/merged_mining/coordinator.py	42.85% <77.77%> (ø)
hathor/client.py	43.52% <81.25%> (ø)
hathor/profiler/cpu.py	50.00% <85.71%> (ø)
hathor/manager.py	69.78% <88.23%> (ø)
hathor/stratum/stratum.py	69.13% <96.55%> (ø)
hathor/api_util.py	91.13% <100.00%> (ø)
... and 106 more