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/install.bat

@@ -0,0 +1,14 @@
+@echo off
+cd %~dp0
+for %%f in (*.hook) do (
+	echo Installing hook: %%~nf
+	copy %%f ..\..\.git\hooks\%%~nf >nul
+)
+for %%f in (*.merge) do (
+	echo Installing merge driver: %%~nf
+	echo [merge "%%~nf"]^
+
+	driver = tools/hooks/%%f %%P %%O %%A %%B %%L >> ..\..\.git\config
+)
+echo Done
+pause