The architectures provided to skipIf / expectedFail are regular
expressions (v. _match_decorator_property() in decorators.py
so on Darwin systems "arm64" would match the skips for "arm" (32-bit
Linux).  Update these to "arm$" to prevent this, and also update
three tests (TestBuiltinFormats.py, TestCrossDSOTailCalls.py,
TestCrossObjectTailCalls.py) that were skipped for arm64 via this
behavior, and need to be skipped or they will fail.

This was moviated by the new TestDynamicValue.py test which has
an expected-fail for arm, but the test was passing on arm64 Darwin
resulting in failure for the CIs.

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

Followup to D127355 and D127378, converting more instances of
assertEqual to assertState.

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

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

It was being used only in some very old tests (which pass even without
it) and its implementation is highly questionable.

These days we have different mechanisms for requesting a build with a
particular kind of c++ library (USE_LIB(STD)CPP in the makefile).

TestCreateDuringInstructionStep have started failing again on
aarch64/linux after moving to new machine. I am going mark it skipped
for aarch64/linux.

There are sporadic failures in this test on arm. I am marking it
skipped as labath suggested flaky decorators no longer work.

This patch marks TestCreateDuringInstructionStep.py as flakey for Linux.
This is failing randomly on arm/aarch64. I will monitor buildbot and
skip it if it fails again.

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