Add "generate function" code action #8279

Job	Run time
validate	17s
test (stable, x86_64-unknown-linux-gnu)	3m 59s
rustfmt	14s
test (stable, x86_64-unknown-linux-musl)	5m 27s
lint-build	52s
test-wasm	1m 34s
test (stable, aarch64-unknown-linux-gnu)	2m 11s
test (stable, aarch64-unknown-linux-musl)	2m 33s
test (stable, x86_64-apple-darwin)	10m 19s
test (stable, x86_64-pc-windows-msvc)	5m 13s
test (stable, aarch64-apple-darwin, macos-latest, arm64, false, true)	3m 39s
test-projects	1m 53s
	38m 11s

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