Add `rb_ec_close` function to manage execution context cleanup. (#15253) #61

Job	Run time
ruby-bench (--zjit-call-threshold=2, --warmup=1 --bench=1, --enable-zjit=dev_nodebug)	19m 45s
cargo clippy	1m 10s
make (zjit-check, --enable-yjit --enable-zjit=dev, 1.85.0)	5m 4s
make (check, --zjit-call-threshold=1, -T --zjit-call-threshold=1, --enable-zjit=dev)	19m 15s
make (btest, --zjit-call-threshold=2, --enable-zjit=dev)	5m 2s
make (check, --zjit-disable-hir-opt --zjit-call-threshold=1, -T --zjit-disable-hir-opt -T --zjit-...	14m 40s
make (zjit-bindgen, To fix: use patch in logs, --enable-zjit=dev --with-gcc=clang-16, /usr/bin/cl...	5m 27s
make (test-bundled-gems, --enable-zjit=dev, --zjit-call-threshold=1)	22m 21s
ZJIT Ubuntu result	2s
	1h 32m 46s

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