Implement STB 34.101.77-2020 `bash` #247

Job	Run time
miri (s390x-unknown-linux-gnu)	1m 1s
miri (x86_64-unknown-linux-gnu)	48s
test-simd	19s
set-msrv / set-msrv	4s
minimal-versions / minimal-versions	24s
test (stable)	20s
test (1.85.0)	15s
build (1.85.0, thumbv7em-none-eabi)	1m 11s
build (stable, thumbv7em-none-eabi)	15s
build (1.85.0, wasm32-unknown-unknown)	19s
build (stable, wasm32-unknown-unknown)	11s
aarch64-sha3 (1.85.0)	41s
aarch64-sha3 (stable)	31s
	6m 19s

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