ci: Add comparative GPU benchmarks on `merge_group` #869

Job	Run time
build	11m 36s
check-lurk-compiles / check-lurk-compiles	1m 30s
code-quality / lints	59s
code-quality / wasm-build	46s
code-quality / msrv	47s
licenses-audits / cargo-deny (advisories, licenses, bans, ...)	42s
link-checker / linkChecker	4s
	16m 24s

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