[MISC] Switch to uv

[sinclert-canonical]

This PR changes the tool used for dependency management from poetry to uv, following this PG-Bouncer example. Some of the main changes are:

• Migrated from poetry-specific pyproject.toml syntax to standard Python project one.
• Migrated from poetry-specific carrot specifier (^) to standard compatible release specifier (~=).
• Renamed dependency groups main to charm and charm-libs to just libs (revertible upon request).

Differences from PG-Bouncer PR:

• The uv binary is installed via pip, instead of via snap (both @paulomach and myself prefer that way).
• The tox_uv.toml file to cherry pick when dependencies are installed from pre-built packages has been ignored. Instead, all tox environments use pre-built packages, only installing from source when the charm gets packed.

Additional changes

• Bumped ruff target python version to 3.10 + updated Python files format.

[carlcsaposs-canonical]

This will cause Dependabot vulnerability alerts to stop working, which Renovate uses to segment security updates from normal PRs (and to open security update PRs immediately, instead of waiting for the weekly schedule)

[sinclert-canonical]

Depends on canonical/data-platform#38.