While testing baremetal lldb, I came across a situation that if an
instruction could not be disassembled, lldb will print nothing as an
output which might be a bit strange. I added at least printing warning
in this case.

assertEquals is a deprecated alias for assertEqual and has been removed
in Python 3.12. This wasn't an issue previously because we used a
vendored version of the unittest module. Now that we use the built-in
version this gets updated together with the Python version used to run
the test suite.

This is an ongoing series of commits that are reformatting our Python
code. Reformatting is done with `black` (23.1.0).

If you end up having problems merging this commit because you have made
changes to a python file, the best way to handle that is to run `git
checkout --ours <yourfile>` and then reformat it with black.

RFC: https://discourse.llvm.org/t/rfc-document-and-standardize-python-code-style

Differential revision: https://reviews.llvm.org/D151460

Eliminate boilerplate of having each test manually assign to `mydir` by calling
`compute_mydir` in lldbtest.py.

Differential Revision: https://reviews.llvm.org/D128077

"A-f" -> "A-F"

Our test infrastructure does not like two tests with the same name, but
it makes sense to do it regardless, as they are testing the same
command.

Also add tests to check that we print the warning in the right
circumstances.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D114877