ci: Add GPU tests on `merge_group` #818

Job	Run time
build	12m 29s
check-lurk-compiles	1m 42s
code-quality / lints	2m 54s
code-quality / msrv	3m 31s
code-quality / wasm-build	1m 27s
link-checker / linkChecker	7s
licenses-audits / cargo-deny (advisories, licenses, bans, ...)	46s
	22m 56s

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