[clang] [llvm] [clang][python][test] Move python binding tests to lit framework (PR #146844)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-s390x-linux-lnt` running on `systemz-1` while building `.github,clang` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/136/builds/4462

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'Clang :: bindings/python/bindings.sh' FAILED ********************
Exit Code: 134

Command Output (stderr):
--
env PYTHONPATH=/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/test/bindings/python/../../../bindings/python    CLANG_LIBRARY_PATH=/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/lib    "/home/uweigand/sandbox/bin/python3.10" -m unittest discover -s /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/test/bindings/python/tests # RUN: at line 30
+ env PYTHONPATH=/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/test/bindings/python/../../../bindings/python CLANG_LIBRARY_PATH=/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/lib /home/uweigand/sandbox/bin/python3.10 -m unittest discover -s /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/test/bindings/python/tests
Invalid CXChildVisitResult!
UNREACHABLE executed at /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/tools/libclang/CIndex.cpp:243!
/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/tools/clang/test/bindings/python/Output/bindings.sh.script: line 1: 1555993 Aborted                 env PYTHONPATH=/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/test/bindings/python/../../../bindings/python CLANG_LIBRARY_PATH=/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/lib "/home/uweigand/sandbox/bin/python3.10" -m unittest discover -s /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/llvm/clang/test/bindings/python/tests

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/146844