feat(csv): expose CsvReadOptions via registerCsv and readCsv

[LantaoJin]

Which issue does this PR close?

• Closes Expose CsvReadOptions via registerCsv and readCsv #22

Summary

Mirror the parquet pattern (#18, #19): add CsvReadOptions builder, four SessionContext methods (registerCsv x2, readCsv x2), and JNI plumbing in native/src/csv.rs. Builder exposes the subset of DataFusion's Rust CsvReadOptions that has a parquet analog already on the Java side -- header, delimiter, quote, escape, terminator, comment, newlinesInValues, schemaInferMaxRecords, fileExtension, fileCompressionType, and explicit Arrow schema.

Tests cover: option-builder fluent API, header-inferred schema with SQL round-trip, explicit-schema header-less file with custom delimiter, and a custom file extension with a tab delimiter.

table_partition_cols, file_sort_order, null_regex and truncated_rows are intentionally deferred -- they have no parquet-side counterpart yet on the Java side.

Changes

• Add CsvReadOptions builder mirroring the subset of Rust
  datafusion::prelude::CsvReadOptions that has a Parquet analog already
  exposed in this repo: header, delimiter, quote, escape, terminator,
  comment, newlinesInValues, schemaInferMaxRecords, fileExtension,
  fileCompressionType, and explicit Arrow schema.
• Add SessionContext.registerCsv(...) / readCsv(...) overloads,
  matching the shape of registerParquet / readParquet.
• Wire native methods through native/src/lib.rs, sharing the
  schema-IPC-serialization helper already used by the Parquet path.

tablePartitionCols, fileSortOrder, nullRegex, and truncatedRows are intentionally deferred to a follow-up; they have no Parquet-side counterpart yet on the Java side and were called out in the issue as out-of-scope.

Test plan

• ./mvnw test — new CsvReadOptionsTest (option-builder) passes.
• ./mvnw test — new SessionContextCsvTest passes:
  • registerCsv + SQL round-trip on an inferred-schema file
  • readCsv with explicit Arrow schema and hasHeader(false)
• make test — full native + JVM build is green.
• cargo fmt and cargo clippy --all-targets -- -D warnings clean under native/.
• ./mvnw spotless:apply clean.

[LantaoJin]

@andygrove glad to see we have a official java binding repo, I'd like to do some contributions.

[andygrove]

LGTM. Thanks @LantaoJin