Add mypy to CI and pre-commit hook

[szabgab]

Introduce running mypy in the pre-commit hook and in the CI (GitHub Actions).
This will ensure no new types of type-annotation issue enters the code-base and it is the first step to enhance the type safety of the Python code.

Starts the work on #3304

PR Checklist:

• Tests that fully cover new/changed functionality.
• Documentation including tutorial content if appropriate.
• Changelogs, if there are API changes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.80%. Comparing base (52a1bcc) to head (64483b1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3305   +/-   ##
=======================================
  Coverage   89.80%   89.80%           
=======================================
  Files          29       29           
  Lines       31026    31026           
  Branches     5679     5679           
=======================================
  Hits        27863    27863           
  Misses       1777     1777           
  Partials     1386     1386           

Flag	Coverage Δ
c-tests	86.85% <ø> (ø)
lwt-tests	80.38% <ø> (ø)
python-c-tests	87.05% <ø> (ø)
python-tests	98.84% <ø> (ø)
python-tests-no-jit	33.60% <ø> (ø)
python-tests-numpy1	50.18% <ø> (ø)

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[benjeffery]

Not planned as discussed in #3304