Swift 6.4.0 Release

What's Changed

• Add explicit typealias to help with borrowing iterator PR by @airspeedswift in #843
• Add test verifying issue #677 by @natecook1000 in #844
• [perf] Flatten DSLTree and implement autopossessification by @natecook1000 in #845
• Revert "[perf] Flatten DSLTree and implement autopossessification" by @artemcm in #847
• Add a code owners file by @natecook1000 in #850
• Skip older Swift versions in CI by @natecook1000 in #846
• Revert the revert of DSL flattening/auto-possessification by @natecook1000 in #849
• Fix forward progress detection by @natecook1000 in #851
• Fix compiler warnings in ByteCodeGen, Compiler, and Regex by @tshortli in #854
• Add GitHub Actions to Dependabot updates by @shahmishal in #860
• Remove DSLNode-based implementation by @natecook1000 in #857
• Reduce amount of \Q...\E quoting in _literalPattern by @natecook1000 in #858
• Bump actions/checkout from 4 to 6 by @dependabot[bot] in #862
• Bump actions/upload-artifact from 4 to 7 by @dependabot[bot] in #861
• Fix a concatenation coalescing issue by @natecook1000 in #859
• [6.4] Fix forward progress check for lookahead, attempt 2 by @natecook1000 in #869

New Contributors

• @airspeedswift made their first contribution in #843
• @artemcm made their first contribution in #847

Full Changelog: swift-6.3.3-RELEASE...swift-6.4.0-RELEASE