feat(core): Add `content_encoding` to `MetaData` #2135

Job	Run time
build_all_features	4m 59s
build_all_platforms (ubuntu-latest)	2m 51s
build_all_platforms (macos-latest)	2m 21s
build_all_platforms (windows-latest)	4m 54s
build_default_features (ubuntu-latest)	33s
build_default_features (macos-latest)	53s
build_default_features (windows-latest)	1m 39s
build_under_wasm	45s
check_clippy	3m 47s
check_docs	3m 28s
check_msrv	30s
unit	6m 54s
	33m 34s

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