Set minimum supported `rust-version` to `1.70` (#1097) #3031

Job	Run time
Cargo check	14m 14s
Check documentation and run doc tests	15m 5s
Cargo clippy	8m 33s
Cargo fmt	36s
Test Light Client	4m 53s
Test non-wasm	8m 23s
Cargo check (WASM)	2m 48s
Test wasm	7m 53s
	1h 2m 25s

Provide feedback