Add yielding support to mlua #1278

Job	Run time
Build (ubuntu-latest, stable, lua54)	3s
Rustfmt	11s
Build (ubuntu-latest, stable, lua53)	19s
Clippy (lua54)	13s
Build (ubuntu-latest, stable, lua52)	23s
Build (ubuntu-latest, stable, lua51)	36s
Clippy (lua53)	14s
Build (ubuntu-latest, stable, luajit)	3s
Clippy (lua52)	12s
Build (ubuntu-latest, stable, luau)	5s
Clippy (lua51)	14s
Build (ubuntu-latest, stable, luau-jit)	5s
Clippy (luajit)	12s
Build (ubuntu-latest, stable, luau-vector4)	5s
Clippy (luau)	15s
Build (macos-latest, stable, lua54)	22s
Clippy (luau-jit)	12s
Build (macos-latest, stable, lua53)	23s
Clippy (luau-vector4)	12s
Build (macos-latest, stable, lua52)	20s
Build (macos-latest, stable, lua51)	21s
Build (macos-latest, stable, luajit)	1s
Build (macos-latest, stable, luau)	1s
Build (macos-latest, stable, luau-jit)	1s
Build (macos-latest, stable, luau-vector4)	28s
Build (windows-latest, stable, lua54)	1s
Build (windows-latest, stable, lua53)	1s
Build (windows-latest, stable, lua52)	1s
Build (windows-latest, stable, lua51)	1s
Build (windows-latest, stable, luajit)	1s
Build (windows-latest, stable, luau)	1s
Build (windows-latest, stable, luau-jit)	1s
Build (windows-latest, stable, luau-vector4)	1s
Cross-compile to aarch64-apple-darwin	0s
Cross-compile to armv7-unknown-linux-gnueabihf	0s
Cross-compile to aarch64-unknown-linux-gnu	0s
Test	0s
Test modules	0s
Test with memory limit	0s
Test with address sanitizer	0s
Test modules on Windows	0s
Test on wasm32-unknown-emscripten	0s
	5m 39s

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