[lldb] Support a Stable ABI LLDB_PYTHON_EXT_SUFFIX (#166269)
When building against the Python Stable API, we should use the `abi3`
ABI tag. Otherwise, Python will refuse to import the native shared
object. This PR adds support for generating a stable ABI compatible
suffix when `LLDB_ENABLE_PYTHON_LIMITED_API` is set.
Previously, on Darwin when building against Python 3.14, you would end
up with `_lldb.cpython-314-darwin.so`. Now, when using the stable ABI,
you get `_lldb.abi3.so` instead. A different version of the Python
interpreter will not consider loading the former, but will load the
latter.