[Android] Remove `AndroidServiceStartType` and update docs #314

Job	Run time
Run Dart Analyzer	41s
Build Android example app (stable channel)	3m 30s
Build iOS example app (3.19)	1m 35s
Build Android example app (3.19)	3m 33s
Build iOS example app (stable channel)	2m 26s
Build macOS example app (3.19)	2m 48s
Build macOS example app (stable channel)	2m 19s
Dart formatting checks	22s
Build Linux example app (3.19)	1m 29s
Build Linux example app (stable channel)	1m 15s
Build Windows example app (3.19)	4m 49s
Build Windows example app (stable channel)	5m 15s
Run all unit tests (Android)	3m 18s
Run all unit tests except for Windows (Dart)	59s
Run integration tests (Android)	13m 33s
Run integration tests (iOS)	3m 5s
Run Windows unit tests (Dart)	3m 19s
	54m 16s

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