Update the Bazaar unit tests to use build_client() and clean up asserts.

Review Request #12502 — Created Aug. 5, 2022 and submitted — Latest diff uploaded


This updates the Bazaar unit tests to build a BazaarClient in each
test where it's needed, rather than in setUp(). This is in prepration
for new tests that will need to handle client construction differently.

The test suite temporarily implements a wrapping build_client()
function that sets the appropriate bzr/brz binary as the default for
the client. When the new dependency code is ready, this function will be

This also cleans up a lot of the assertions to be less verbose, and
more specific. We had a lot of combinations of checking instance type,
key presence, and then values, but this is far less useful (less
accurate) than just checking dictionaries for equality. Given the work
being done already in each function, I felt this was the best time to
clean this code up.

All unit tests pass.