move `fetch metadata` to a separate crate `subxt_utils_fetchmetadata` #5395

Job	Run time
Cargo fmt	27s
Check unused dependencies	1m 5s
Cargo clippy	5m 29s
Cargo check	9m 31s
Check documentation and run doc tests	7m 29s
Cargo check (WASM)	1m 20s
Cargo clippy (WASM)	1m 6s
Test (no_std)	1m 59s
Test (Light Client)	4m 35s
Test (WASM)	11m 42s
Test (Native)	16m 29s
Test chainhead backend	17m 29s
	1h 18m 41s

Provide feedback