chore: Refactored dependencies management and fixed linters configurations

[svdimchenko]

I've implemented the following optimisations and fixes:

• generalised dependencies in pyproject.toml (before there was extra dev-requirements.txt file)
• enabled mypy check (it was somehow disabled at all)
  Found 408 errors in 74 files (checked 149 source files)
• enabled black (seems it was disabled as well)
• bumped pre-commit hooks to the latest versions

TODO:
the following flags shoould be removed and corresponding code fixed:
--strict (to enable)
--allow-untyped-defs (to remove)
--allow-untyped-call (to remove)

[haritamar]

HI @svdimchenko ,
Wow, thanks for all this effort, sorry for the late response.
We've accumulated some backlog in our PRs that we're just getting into.

Admittedly though, I don't feel very comfortable with merging this PR since it's pretty huge and touches a lot of code.

I think we'll likely incorporate some of the changes into separate, smaller PRs:

• Moving dev-requirements to poetry.
• Upgrading some of the pre-commit versions

Changes I'm less sure about:

• Moving mypy configuration to pyproject.toml - what is the motivation? I think in particular the configuration file allowed us to only ignore missing imports for specific packages that don't have stubs.
• Changing line lengths in black and flake to 120 - mainly because it's not aligned with a separate internal repo we have, and not sure it's important enough given the amount of changes it's producing / messing git blame.

Also curious about your comment that mypy and black were disabled - that's interesting, they definitely do run regularly in our pre-commits and CI. Where did you see that they were disabled?

For now though I'm closing this PR.