perf(statedb): avoid allocations in cache type comparison

[wangjingshuiku]

Proposed changes

Use strings.EqualFold when matching configured trie-node cache types instead of allocating lower-cased copies of both operands for every candidate. Accepted values and the canonical enum value returned by ToValid are unchanged.

Types of changes

• 🐛 Bug fix
• ✨ Non-hardfork changes (node upgrade not required)
• 💥 Hardfork / consensus-breaking changes
• 🧪 Test improvements
• 🧰 CI / build tool
• ♻️ Chore / Refactor / Non-functional changes

Checklist

• 📖 I have read the CONTRIBUTING GUIDELINES document
• 📝 I have signed the CLA statement if this is my first contribution
• 🟢 Lint and unit tests pass locally with my changes (make test)

Targeted compilation check completed:
go test ./storage/statedb -run '^$'

Related issues

None.

Further comments

This is a non-functional allocation reduction in a small case-insensitive comparison loop.

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[wangjingshuiku]

I have read the CLA Document and I hereby sign the CLA