fix(whiteboard) simplify room hash generation to cover custom region shards #13173

Job	Run time
Build mobile bundle (Android)	2m 50s
Build Frontend (macos-latest)	7m 9s
Build Frontend (ubuntu-latest)	4m 16s
Build mobile bundle (iOS)	3m 27s
Lint	2m 22s
Build mobile SDK (iOS)	10m 35s
Build mobile SDK (Android)	6m 45s
Test Debian packages build	9m 16s
	46m 40s

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