feat(core/services-gcs): support user defined metadata #1970

Job	Run time
build_all_features	5m 15s
build_all_platforms (ubuntu-latest)	2m 49s
build_all_platforms (macos-latest)	2m 57s
build_default_features (ubuntu-latest)	41s
build_under_wasm	50s
build_all_platforms (windows-latest)	6m 6s
build_default_features (macos-latest)	39s
build_default_features (windows-latest)	1m 53s
check_clippy	4m 4s
check_docs	3m 39s
unit	6m 38s
check_msrv	32s
	36m 3s

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