feat: Add lance_search support for {vector,full-text,fuzzy} search

[Xuanwo]

This PR will add lance_search support for {vector,full-text,fuzzy} search.

Close #44

Full-text search (FTS)

-- Search a text column, returning BM25-like scores in `_score`
SELECT id, text, _score
FROM lance_search('path/to/dataset.lance', 'puppy', text_column = 'text', k = 10, prefilter = true)
ORDER BY _score DESC;

Structured text queries

-- Equivalent to the plain string form, but explicit about the target column
SELECT id, text, _score
FROM lance_search('path/to/dataset.lance', lance_match_query('crazily', 'text'), k = 100)
ORDER BY _score DESC;

Vector search

-- Search a vector column, returning distances in `_distance` (smaller is closer)
SELECT id, label, _distance
FROM lance_search(
  'path/to/dataset.lance',
  [0.1, 0.2, 0.3, 0.4]::FLOAT[],
  vector_column = 'vec',
  k = 5,
  prefilter = true
)
ORDER BY _distance ASC;

Hybrid search (vector + FTS)

-- Combine vector and text scores, returning `_hybrid_score` in addition to `_distance` / `_score`
SELECT id, _hybrid_score, _distance, _score
FROM lance_search(
  'path/to/dataset.lance',
  lance_hybrid_query([0.1, 0.2, 0.3, 0.4]::FLOAT[], 'puppy', 'vec', 'text', 0.5, 4),
  k = 10,
  prefilter = false
)
ORDER BY _hybrid_score DESC;

---

Parts of this PR were drafted with assistance from Codex (with gpt-5.2) and fully reviewed and edited by me. I take full responsibility for all changes.