Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>

assertRegexpMatches is a deprecated alias for assertRegex 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

This uses the same approach as the debug info tests to avoid needing to
explicitly spell out the two kinds of tests. I convert a handful of
tests to the new mechanism. The rest will be converted in follow-up
patches.

Nearly all of our lldb-server tests have two flavours (lldb-server and
debugserver). Each of them is tagged with an appropriate decorator, and
each of them starts with a call to a matching "init" method. The init
calls are mandatory, and it's not possible to meaningfully combine them
with a different decorator.

This patch leverages the existing decorators to also tag the tests with
the appropriate debug server tag, similar to how we do with debug info
flavours. This allows us to make the "init" calls from inside the common
setUp method.

Summary: Moves lldbsuite tests to lldb/test/API.

This is a largely mechanical change, moved with the following steps:

```
rm lldb/test/API/testcases
mkdir -p lldb/test/API/{test_runner/test,tools/lldb-{server,vscode}}
mv lldb/packages/Python/lldbsuite/test/test_runner/test lldb/test/API/test_runner
for d in $(find lldb/packages/Python/lldbsuite/test/* -maxdepth 0 -type d | egrep -v "make|plugins|test_runner|tools"); do mv $d lldb/test/API; done
for d in $(find lldb/packages/Python/lldbsuite/test/tools/lldb-vscode -maxdepth 1 -mindepth 1 | grep -v ".py"); do mv $d lldb/test/API/tools/lldb-vscode; done
for d in $(find lldb/packages/Python/lldbsuite/test/tools/lldb-server -maxdepth 1 -mindepth 1 | egrep -v "gdbremote_testcase.py|lldbgdbserverutils.py|socket_packet_pump.py"); do mv $d lldb/test/API/tools/lldb-server; done
```

lldb/packages/Python/lldbsuite/__init__.py and lldb/test/API/lit.cfg.py were also updated with the new directory structure.

Reviewers: labath, JDevlieghere

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D71151