Add getSchema() to Records for schema access with empty results

[PierceAndy]

Summary

Add getSchema() method to Records class to enable access to table schema metadata even when query results are empty.

Following the pattern from PR #2004, this change exposes the TableSchema from the underlying ClickHouseBinaryFormatReader, making it consistent with GenericRecord.getSchema().

Use case: When queryRecords() or queryAll() returns no rows, users can still inspect column metadata (names, types, etc.) without needing to iterate through records.

Example:

Records records = client.queryRecords("SELECT * FROM table WHERE 1=0").get();
if (records.isEmpty()) {
    TableSchema schema = records.getSchema();
    schema.getColumns().forEach(col ->
        System.out.println(col.getColumnName() + ": " + col.getDataType())
    );
}

Checklist

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG

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CHANGELOG entry:

* Add `Records.getSchema()` method to access table schema from query results, including empty result sets

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Note

Low Risk
Low risk API addition that delegates to the existing binary reader schema with only new test coverage; minimal impact beyond adding a new method.

Overview
Adds Records.getSchema() to return the underlying TableSchema, enabling schema inspection even when Records.isEmpty() is true.

Extends QueryTests with integration coverage for getSchema() on both empty and non-empty result sets, and asserts records’ per-row schema matches the collection schema.

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[CLAassistant]

All committers have signed the CLA.

[chernser]

@PierceAndy,

thank you for the contribution!