Python: Move Python language pack tooling to external repo

This is essentially the contents of `language-packs/python/tools` with some minor
modifications to account for the changed location.

Of note: we explicitly exclude the `recorded-call-graph-metrics` director that
was already present in `python/tools`. When we revisit this directory for some
cleanup (e.g. to get rid of the `lgtm` references), we'll probably want to switch
to an explicit list of sources to include.

python/tools/lgtm-scripts/python_setup.sh

@@ -0,0 +1,5 @@
+#! /bin/bash
+
+set -eu
+
+python "${CODEQL_EXTRACTOR_PYTHON_ROOT}/tools/setup.py" || true