Adds observer UI button for toggling HUDs #18490

Job	Run time
Lint with OpenDream	1m 36s
Compile Maps	1m 42s
Run Linters	1m 19s
Find Maps to Test	10s
Windows Build	1m 50s
Alternate Tests (515, 1610, lv624) / run_unit_tests	6m 50s
Unit Tests (almayer) / run_unit_tests	5m 54s
Unit Tests (bigredv2) / run_unit_tests	6m 7s
Unit Tests (chinook) / run_unit_tests	6m 42s
Unit Tests (corsat) / run_unit_tests	6m 16s
Unit Tests (fiorina_sciannex) / run_unit_tests	5m 56s
Unit Tests (ice_colony_v2) / run_unit_tests	6m 36s
Unit Tests (desert_dam) / run_unit_tests	5m 57s
Unit Tests (kutjevo) / run_unit_tests	5m 52s
Unit Tests (lv522_chances_claim) / run_unit_tests	6m 37s
Unit Tests (lv624) / run_unit_tests	5m 55s
Unit Tests (new_varadero) / run_unit_tests	6m 15s
Unit Tests (prison_station_fop) / run_unit_tests	6m 39s
Unit Tests (runtime) / run_unit_tests	6m 30s
Unit Tests (shivas_snowball) / run_unit_tests	6m 14s
Unit Tests (sorokyne_strata) / run_unit_tests	6m 24s
Unit Tests (whiskey_outpost_v2) / run_unit_tests	6m 3s
Check Alternate Tests	1s
	1h 53m 25s

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