Implement Display trait for string::Match #2167

Job	Run time
testfull-regex-automata	8m 14s
test (stable, ubuntu-latest, stable)	3m 43s
miri-regex-automata	9m 26s
test (stable-32, ubuntu-latest, stable, i686-unknown-linux-gnu)	2m 55s
msrv	3m 48s
rustfmt	6s
test (stable-powerpc64, ubuntu-latest, stable, powerpc64-unknown-linux-gnu)	7m 32s
test (stable-s390x, ubuntu-latest, stable, s390x-unknown-linux-gnu)	9m 27s
testfull-regex	3m 57s
test (beta, ubuntu-latest, beta)	3m 50s
testfull-regex-capi	20s
testfull-regex-syntax	2m 0s
test (nightly, ubuntu-latest, nightly)	3m 42s
test (macos, macos-latest, stable)	8m 43s
test (win-msvc, windows-latest, stable)	6m 9s
test (win-gnu, windows-latest, stable-x86_64-gnu)	3m 33s
	1h 17m 25s

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