feat(core/services-gcs): support user defined metadata #1972

Job	Run time
check_clippy	4m 1s
check_docs	3m 42s
check_msrv	36s
build_all_features	5m 24s
build_all_platforms (ubuntu-latest)	2m 40s
build_all_platforms (macos-latest)	3m 34s
build_default_features (ubuntu-latest)	42s
build_all_platforms (windows-latest)	5m 13s
build_default_features (macos-latest)	1m 4s
build_default_features (windows-latest)	3m 4s
build_under_wasm	52s
unit	6m 3s
	36m 55s

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