ci: Migrate Gitlab tests to GitHub runner #6

# to view logs

Job	Run time
Get HEAD commit message	1s
Check formatting	1m 16s
Run Clippy checks	15m 11s
Run Chopsticks tests	36m 13s
Run Clippy checks (--all-features)	15m 0s
Run Cargo tests	23m 27s
Check Rustdoc	14m 52s
Run Cargo tests (--all-features)	18m 27s
Run try-runtime (peregrine)	15m 55s
Check Rustdoc (--all-features)	15m 22s
Run try-runtime (spiritnet)	15m 59s
	2h 51m 43s

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