* 12175 add rack starting unit
* 12175 rack starting unit to svg
* verify devices can still fit if change rack starting_unit
* 12175 fix migration
* 12175 fix typo and test
* 12175 fix test
* 12175 fix max height calc display
* Misc cleanup & fixes
---------
Co-authored-by: Jeremy Stretch <jstretch@netboxlabs.com>
