`pudb.run`: Expose version information (#528)

* `pudb.run`: Expose version information

Calling `python -m pudb.run -v` (**exactly!**), or using `--version` flag,
it prints the version information and exits.

Additionally, added tests to safeguard functionality.

Fixes https://github.com/inducer/pudb/discussions/527



Signed-off-by: Stavros Ntentos <133706+stdedos@users.noreply.github.com>

* flake8 E501

Signed-off-by: Stavros Ntentos <133706+stdedos@users.noreply.github.com>

Co-authored-by: Stavros Ntentos <11300730-stavros-relex@users.noreply.gitlab.com>