api: add SetMatches::matched_all #2423

Job	Run time
testfull-regex-automata	9m 21s
msrv	1m 0s
testfull-regex	4m 0s
testfull-regex-capi	25s
test (stable, ubuntu-latest, stable)	3m 44s
test (stable-32, ubuntu-latest, stable, i686-unknown-linux-gnu)	2m 50s
testfull-regex-syntax	1m 56s
test (stable-powerpc64, ubuntu-latest, stable, powerpc64-unknown-linux-gnu)	7m 47s
miri-regex-automata	14m 11s
test (stable-s390x, ubuntu-latest, stable, s390x-unknown-linux-gnu)	9m 5s
rustfmt	8s
test (beta, ubuntu-latest, beta)	3m 43s
test (nightly, ubuntu-latest, nightly)	2m 57s
test (macos, macos-latest, stable)	2m 25s
test (win-msvc, windows-latest, stable)	7m 32s
test (win-gnu, windows-latest, stable-x86_64-gnu)	3m 38s
	1h 14m 42s

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