Add a new and improved mapmerge (#33869)

Key benefits of the new mapmerge include: multi-Z support, effective
reuse of deleted keys, automatic handling of key overflow, and utilizing
a git pre-commit hook to eliminate the need to run batch files manually.

tools/hooks/python.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+set -e
+if command -v python3 >/dev/null 2>&1; then
+	PY=python3
+else
+	PY=python
+fi
+PATHSEP=$($PY - <<'EOF'
+import sys, os
+if sys.version_info.major != 3 or sys.version_info.minor < 6:
+	sys.stderr.write("Python 3.6+ is required: " + sys.version + "\n")
+	exit(1)
+print(os.pathsep)
+EOF
+)
+export PYTHONPATH=tools/mapmerge2/${PATHSEP}${PYTHONPATH}
+$PY "$@"