2.1.3: Fixed memory leaks with invalid inputs

Fixed memory leaks reported by ruby_memcheck when rewinding an RE2::Scanner and when passing invalid input to RE2::Regexp#scan, RE2::Regexp#initialize, RE2.Replace, RE2.GlobalReplace and RE2::Set#add.

Thanks to @peterzhu2118 for maintaining ruby_memcheck and their assistance in finding the source of these leaks.

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SHA256 checksums:

27316bb47cfc0f28cfd1626426120e1c55ca8420a64c9e966f8feb1c911eae2a  re2-2.1.3-aarch64-linux.gem
81ffdd76b202f24461b4868abed96c994e2106e57970004b841499da983f688c  re2-2.1.3-arm-linux.gem
86d553e85779943a353865cbfdd89156c0411b92a1c7fe6abf1024135d53190e  re2-2.1.3-arm64-darwin.gem
be0277c15bef6f38a2f9805aca798de4a31f6319cb1790ff6683112cb89721da  re2-2.1.3-x64-mingw-ucrt.gem
cadba41d90f2186507c97593084b8f951c9c3ee7ecb2be02f3497aa9c5cdaadb  re2-2.1.3-x64-mingw32.gem
ad54cafdaf40310cf3aab485697b997718c573d6a780f802c3faab7a38119623  re2-2.1.3-x86-linux.gem
6bfa3c1c119b485375688a9c90c0b8cfc03991495c2e4d50accb6bbcd406c186  re2-2.1.3-x86-mingw32.gem
513b12c5b7536c65e80ddb2a7eee0dbbefea534d6352e9470040016c547f90a5  re2-2.1.3-x86_64-darwin.gem
73a2e20fc1dc7b2773d2862ec061e545f6820643486c0d69e3ad40de19ce5c0b  re2-2.1.3-x86_64-linux.gem
03a30b53002ab66b66fa2d4500c82ec0866020c22e11c23516f660ce43cfae8f  re2-2.1.3.gem