refactor: Replace enhanced enum with native dart enum #1850

Job	Run time
dart / dart_analyzer	40s
app_jobs / dart_web_compatible	57s
app_jobs / coverage	1h 35m 50s
app_jobs / database_web_tests	1m 3s
app_jobs / coverage_without_olm	2m 26s
app_jobs / e2ee_test (synapse)	2m 18s
app_jobs / pub-dev-dry-run	30s
app_jobs / e2ee_test (dendrite)	1m 48s
app_jobs / e2ee_test (conduit)	2m 14s
general / conventional_commits	3s
app_jobs / merge_converage	1s
app_jobs / review_app_coverage	1s
	1h 47m 51s

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