feat(fs-router): change dollar to at in special filenames #5398

Job	Run time
Build Java and TypeScript for other tasks	2m 26s
Test Java	3m 31s
Check style	1m 41s
Gradle tests (ubuntu-latest)	3m 24s
ITs (ubuntu-latest, group-1)	4m 47s
Gradle tests (windows-latest)	7m 45s
ITs (ubuntu-latest, group-2)	5m 52s
ITs (windows-latest, some)	6m 55s
Test TypeScript	2m 7s
Tests Summary	2s
	38m 30s

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