chore: moved user agent to logging category api #1943

Job	Run time
test / test-dart-vm (3.0.1)	3m 56s
test / test-dart-vm (stable)	3m 54s
ddc_test / test-dart-ddc (3.0.1, chrome)	4m 51s
ddc_test / test-dart-ddc (3.0.1, firefox)	4m 42s
ddc_test / test-dart-ddc (stable, chrome)	4m 19s
dart2js_test / test-dart-2js (3.0.1, chrome)	6m 21s
native_test / test-dart-native (macos-latest)	7m 10s
ddc_test / test-dart-ddc (stable, firefox)	4m 32s
dart2js_test / test-dart-2js (3.0.1, firefox)	6m 26s
native_test / test-dart-native (windows-latest)	7m 10s
dart2js_test / test-dart-2js (stable, chrome)	6m 20s
dart2js_test / test-dart-2js (stable, firefox)	5m 58s
	1h 5m 39s

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