fix(table): resolve dropped equality fields from schema history

[mattfaltyn]

Fixes #1951.

Summary

• resolve equality-delete fields against the newest table schema that contains the complete key when those fields are absent from the current schema
• load schema history only for scans whose equality keys are missing from the current schema
• extend the equality-delete round trip to drop the key and verify a surviving-column projection still applies the delete

Why

Equality delete files retain stable table field IDs after schema evolution. The reader previously resolved those IDs only against the current schema, so dropping a live equality key made affected scans fail before filtering.

Using the newest historical schema that contains the delete file's complete key preserves field identity and keeps the current result projection unchanged.

Testing

• go test ./table -run '^TestEqualityDeleteReadRoundTrip$' -count=2 -v
• go test ./table -run 'EqualityDelete' -count=1
• go test -race ./table -run '^TestEqualityDeleteReadRoundTrip$' -count=1
• go vet ./table
• make test
• make lint
• make test-race
• make test-assert