Install `secondprog` to the remote target if necessary.

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

If this test fails, the error message isn't helpful:

```
self.assertEqual(len(threads), 1,
AssertionError: 0 != 1 : Stopped at breakpoint in exec'ed process
```

This change adds asserts to verify that:
1. The process is stopped
2. For each thread, that the stop reason is None, or Breakpoint

The latter will indicate if execution has stopped for some other reason, and if so what
that reason is.

Differential Revision: https://reviews.llvm.org/D148588

Not needed now that we require python 3.

Reviewed By: kastiglione, JDevlieghere

Differential Revision: https://reviews.llvm.org/D131761

I accidentally forgot to stage part of the changes in the previous
commit.

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

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

Follow to D127355, converting more `assertEquals` to `assertState`.

Differential Revision: https://reviews.llvm.org/D127378

Follow up to D95813, this converts multiline assertTrue to assertEqual.

Differential Revision: https://reviews.llvm.org/D95899

Convert `assertTrue(a == b)` to `assertEqual(a, b)` to produce better failure messages.

These were mostly done via regex search & replace, with some manual fixes.

Differential Revision: https://reviews.llvm.org/D95813