Allow explicit values with `uv version --bump` (#16555)
Resolves https://github.com/astral-sh/uv/issues/16427
This PR updates `uv version --bump` so you can pin the exact number
you’re targeting, i.e. `--bump patch=10` or `--bump dev=42`. The
command-line interface now parses those `component=value` flags, and the
bump logic actually sets the version to the number you asked for.
