[Bug #20992] Test for local variable name encodings #529

Job	Run time
cargo test	57s
cargo clippy	35s
make (yjit-bindgen, To fix: use patch in logs, --with-gcc=clang-12 --enable-yjit=dev)	4m 19s
make (check, RUSTC='rustc +1.58.0', 1.58.0)	8m 50s
make (check, --enable-yjit=dev)	12m 25s
make (check, --enable-yjit=dev, --yjit-call-threshold=1 --yjit-verify-ctx --yjit-code-gc, -T --yj...	14m 53s
make (test-bundled-gems, --enable-yjit=dev)	18m 47s
make (yjit-bench, --enable-yjit=dev, --yjit-stats, true)	6m 5s
YJIT Ubuntu result	1s
	1h 6m 52s

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