feat: add text field weights support to TextQuery (#384)

[bsbodden]

Implements text field weights functionality allowing users to prioritize certain fields over others in full-text search queries.

Python Reference: PR #384 (redis/redis-vl-python#384)
Test Reference: tests/unit/test_text_query_weights.py (123 lines)

Implementation:

• TextQuery now accepts Map<String, Double> for textFieldWeights
• Builder pattern with textField() for single field (backward compatible)
• Builder method textFieldWeights() for multiple fields with custom weights
• Query syntax: @field:(terms) => { $weight: 5.0 } for non-default weights
• Multiple fields joined with OR operator in parentheses
• Dynamic weight updates via setFieldWeights() method

Validation:

• Rejects negative weights (IllegalArgumentException)
• Rejects zero weights (IllegalArgumentException)
• Ensures all weights are positive numbers
• Maintains backward compatibility with single string field API

Breaking Changes:

• TextQuery constructor changed to private (use Builder instead)
• Updated QueryIntegrationTest to use builder pattern

Tests: 7 unit tests added (TextQueryWeightsTest)

• testTextQueryAcceptsWeightsDict
• testTextQueryGeneratesWeightedQueryString
• testTextQueryMultipleFieldsWithWeights
• testTextQueryBackwardCompatibility
• testTextQueryRejectsNegativeWeights
• testTextQueryRejectsZeroWeights
• testSetFieldWeightsMethod

All tests pass: 289 tests, 14 skipped

Files Modified:

• core/src/main/java/com/redis/vl/query/TextQuery.java (complete rewrite)
• core/src/test/java/com/redis/vl/query/QueryIntegrationTest.java (builder migration)

Files Created:

• core/src/test/java/com/redis/vl/query/TextQueryWeightsTest.java