fuzz: add regression test

This adds a regression test for a bug found in the *old* regex crate
that isn't present with the regex-automata rewrite. I discovered this
while doing differential fuzzing. I didn't do a root cause analysis of
the bug, but my guess is a literal optimization problem.

testdata/regression.toml

@@ -719,3 +719,12 @@ name = "negated-unicode-word-boundary-dfa-fail"
 regex = '\B.*'
 haystack = "!\u02D7"
 matches = [[0, 3]]
+
+# This failure was found in the *old* regex crate (prior to regex 1.9), but
+# I didn't investigate why. My best guess is that it's a literal optimization
+# bug. It didn't occur in the rewrite.
+[[test]]
+name = "missed-match"
+regex = 'e..+e.ee>'
+haystack = 'Zeee.eZZZZZZZZeee>eeeeeee>'
+matches = [[1, 26]]