Use ALWAYS_INLINE for vm_getinstancevariable #329

Job	Run time
make (check, --enable-yjit, --yjit)	5m 34s
make (check, --enable-yjit=dev, --yjit-call-threshold=1 --yjit-verify-ctx --yjit-code-gc, -T --yj...	12m 10s
cargo test	46s
YJIT macOS result	3s
	18m 33s

Provide feedback