Combine rb_imemo_tmpbuf_auto_free_pointer and rb_imemo_tmpbuf_new #608

Job	Run time
cargo clippy	32s
cargo test	46s
make (check, RUSTC='rustc +1.58.0', 1.58.0)	8m 52s
make (check, --enable-yjit=dev, --yjit-call-threshold=1 --yjit-verify-ctx --yjit-code-gc, -T --yj...	17m 55s
make (test-bundled-gems, --enable-yjit=dev)	25m 16s
make (yjit-bindgen, To fix: use patch in logs, --with-gcc=clang-14 --enable-yjit=dev, /usr/lib/ll...	5m 17s
make (check, --enable-yjit=dev)	13m 16s
YJIT Ubuntu result	4s
	1h 11m 58s

Provide feedback