Introduce shellcheck to lint shell scripts #12893

Job	Run time
check_format	1m 40s
x86_64-gnu-test (1.7.3)	35m 3s
x86_64-gnu-test (1.8.2)	34m 42s
x86_64-gnu-test (1.9.2)	34m 30s
x86_64-gnu-test (1.10.1)	35m 25s
x86_64-gnu-test (1.11.2)	35m 54s
x86_64-gnu-test (1.12.2)	34m 45s
x86_64-gnu-test (1.13.3)	34m 4s
x86_64-gnu-test-preview_mt	5m 53s
x86_64-gnu-test (1.14.0)	35m 43s
x86_64-musl-test	39m 17s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	34m 32s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	35m 6s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	35m 13s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	33m 31s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	32m 55s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	32m 40s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	33m 47s
	9h 24m 40s

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