bundlespec: rationalize the way we specify stream bundle version Instead of having weird dedicated option for each version (v2, v3, etc) we reuse the same "stream" parameters. This is consistent with the ability to request a stream clone using "none-v2;stream=v2". This changeset introduce no user visible change, this is pure internal cleaning.

To run the tests, do:

cd tests/
python run-tests.py

See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.