the function signature for `GetStopDescription` is
`lldb::SBThread::GetStopDescription(char *dst_or_null, size_t len)`.
To get a description you need to call the function first time to get the
buffer size. a second time to get the description.

This is little worse from the python size as the signature is
`lldb.SBThread.GetStopDescription(int: len) -> list[str]` the user has
to pass the max size as possible with no way of checking if it is
enough.

This patch adds a new api
`lldb.SBThread.GetStopDescription(desc: lldb.SBStream()) -> bool` `bool
lldb::SBThread::GetStopDescription(lldb::SBStream &description)` which
handles this case.

Adds new Test case for lua.

When SWIG is installed but not any Lua interpreter, the cmake script in
`lldb/cmake/modules/FindLuaAndSwig.cmake` will execute
`find_program(LUA_EXECUTABLE, ...)` and this will set the
`LUA_EXECUTABLE` variable to `LUA_EXECUTABLE-NOTFOUND`.

Ensure that in this case we are skipping the Lua tests requiring the
interpreter.

Lua 5.3 and Lua 5.4 are similar enough that we can easily support both
in LLDB. This patch adds support for building LLDB with both and updates
the documentation accordingly.

 - Explicitly create an `SBFile`.
 - Add missing call to `close`.
 - Use `SetErrorFile` in TestLegacyFileErr.

from PEP8
(https://peps.python.org/pep-0008/#programming-recommendations):

> Comparisons to singletons like None should always be done with is or
is not, never the equality operators.

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

This uses [teyit](https://pypi.org/project/teyit/) to modernize asserts,
as recommended by the [unittest release
notes](https://docs.python.org/3.12/whatsnew/3.12.html#id3).

For example, `assertTrue(a == b)` is replaced with `assertEqual(a, b)`.
This produces better error messages, e.g. `error: unexpectedly found 1
and 2 to be different` instead of `error: False`.

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

In API tests, replace use of the `p` alias with the `expression` command.

To avoid conflating tests of the alias with tests of the expression command,
this patch canonicalizes to the use `expression`.

Differential Revision: https://reviews.llvm.org/D141539

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

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