fix(oracle): parse extract and interval partition gaps

[rebelice]

Summary

• Add Oracle AST/parser support for EXTRACT(datetime_field FROM expr) in expression contexts, including function-based indexes.
• Add ANSI datetime literal parsing for DATE 'YYYY-MM-DD' and TIMESTAMP '...' expression forms.
• Add range interval partition clause parsing with regression coverage, while preserving failure for interval partitioning without required range partitions.

Test Plan

• go test ./oracle/parser -run 'TestCreateIndexFunctionBasedExtract|TestCreateTableIntervalPartitioning|TestCreateTableDateLiteralPartitionBound' -count=1
• go test ./oracle/parser -count=1
• go test ./oracle/... -count=1