feat(storage): multi bucket download file api #3909

Job	Run time
test / test-dart-vm (3.3.0)	2m 31s
test / test-dart-vm (stable)	2m 6s
native_test / test-dart-native (macos-14)	2m 8s
dart2js_test / test-dart-2js (3.3.0, chrome)	4m 16s
ddc_test / test-dart-ddc (3.3.0, chrome)	3m 34s
native_test / test-dart-native (windows-latest)	5m 29s
dart2js_test / test-dart-2js (3.3.0, firefox)	4m 29s
ddc_test / test-dart-ddc (3.3.0, firefox)	4m 12s
dart2js_test / test-dart-2js (stable, chrome)	3m 55s
dart2js_test / test-dart-2js (stable, firefox)	4m 9s
ddc_test / test-dart-ddc (stable, chrome)	3m 39s
ddc_test / test-dart-ddc (stable, firefox)	4m 1s
	44m 29s

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