Migrate custom error trait impls to `thiserror` #5432

Job	Run time
Check unused dependencies	28s
Cargo fmt	21s
Cargo clippy	4m 59s
Cargo check	4m 49s
Cargo check (WASM)	1m 35s
Check documentation and run doc tests	4m 47s
Cargo clippy (WASM)	1m 34s
Test (WASM)	1s
Test chainhead backend	1s
Test (no_std)	1s
Test (Light Client)	1s
Test (Native)	1s
	18m 38s

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