Add "generate function" code action #8280

Job	Run time
lint-build	50s
rustfmt	13s
test (stable, x86_64-unknown-linux-gnu)	3m 35s
test-wasm	1m 24s
test (stable, x86_64-unknown-linux-musl)	5m 32s
validate	18s
test (stable, aarch64-unknown-linux-gnu)	2m 28s
test (stable, aarch64-unknown-linux-musl)	2m 42s
test (stable, x86_64-apple-darwin)	8m 47s
test (stable, x86_64-pc-windows-msvc)	6m 30s
test (stable, aarch64-apple-darwin, macos-latest, arm64, false, true)	3m 50s
test-projects	1m 49s
	37m 58s

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