[clang] [llvm] Enable LLDB tests in pre-merge CI (PR #94208)

[David Spickett via cfe-commits]

DavidSpickett wrote:

And I would bet that a majority of the unresolved are due to:
```
ModuleNotFoundError: No module named 'pexpect'
```
You can either install it with `pip` or pass `-DLLDB_TEST_USER_ARGS=--skip-category=pexpect` to CMake.

https://github.com/llvm/llvm-project/pull/94208