[MANUAL MIRROR] Use portable Python for map merge hooks, other tools / Add .dmm merge driver (#2681)

* Use portable Python for map merge hooks, other tools (#55658)

* Add .dmm merge driver (#55699)

This is kind of a prototype. It only fully handles a few situations, 
and doesn't produce particularly easy-to-read conflict markers when it 
fails. I hope that it can be useful at least some of the time, can be 
improved over time, and that the lessons learned can influence a future 
interactive GUI conflict resolver (integrated into StrongDMM?). In the 
worst case, one can fall back to the tried and true "manually re-do one 
side's changes" strategy. 

**Automatic use**: In `tools/hooks/`, run `Install.bat`

**Manual use**, for Git GUIs that don't run merge drivers: while a 
merge is in progress, in `tools/mapmerge2/`, double-click `Resolve Map 
Conflicts.bat`

This PR also removes the error-prone "Prepare Maps.bat" / 
"mapmerge.bat" workflow. Those who aren't using the hooks should 
instead use `Run Before Committing.bat` before committing. First-time 
contributors who opened a PR without map merging can be advised to run 
`I Forgot To Map Merge.bat`.

* Fix loose double-quot in tradership_faction.dmm

Co-authored-by: Tad Hardesty <tad@platymuus.com>

tools/bootstrap/python.bat

@@ -0,0 +1 @@
+@call powershell.exe -NoLogo -ExecutionPolicy Bypass -File "%~dp0\python_.ps1" %*