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 is a regression since:
  [lldb][NFC] Modernize lang/cpp/scope test
  acb0b99c8e4f1dc65a7f1e26da9db77239a67da7
  rGacb0b99c8e4f

  File "/home/jkratoch/redhat/llvm-monorepo/lldb/test/API/lang/cpp/scope/TestCppScope.py", line 19, in test
    self.assertEqual(global_var_names, expected_var_names)
  AssertionError: Lists differ: ['C::a', 'A::a', 'B::a', '::a'... != ['A::a', 'B::a', 'C::a', '::a'...
  First differing element 0:
  C::a
  A::a
  - ['C::a', 'A::a', 'B::a', '::a']
  + ['A::a', 'B::a', 'C::a', '::a']

ManualDWARFIndex using NameToDIE does not sort alphabetically:
    // This is only for uniqueness, not lexicographical ordering, so we can
    // just compare pointers.
    return uintptr_t(lhs.GetCString()) < uintptr_t(rhs.GetCString());

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