feat: add name parameter to remaining Python create index calls (#2617)

## Summary
This PR adds the missing `name` parameter to `create_scalar_index` and
`create_fts_index` methods in the Python SDK, which was inadvertently
omitted when it was added to `create_index` in PR #2586.

## Changes
- Add `name: Optional[str] = None` parameter to abstract
`Table.create_scalar_index` and `Table.create_fts_index` methods
- Update `LanceTable` implementation to accept and pass the `name`
parameter to the underlying Rust layer
- Update `RemoteTable` implementation to accept and pass the `name`
parameter
- Enhanced tests to verify custom index names work correctly for both
scalar and FTS indices
- When `name` is not provided, default names are generated (e.g.,
`{column}_idx`)

## Test plan
- [x] Added test cases for custom names in scalar index creation
- [x] Added test cases for custom names in FTS index creation  
- [x] Verified existing tests continue to pass
- [x] Code formatting and linting checks pass

This ensures API consistency across all index creation methods in the
LanceDB Python SDK.

Fixes #2616

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude <noreply@anthropic.com>

python/python/tests/test_fts.py

@@ -157,7 +157,16 @@ def test_create_index_with_stemming(tmp_path, table):
 def test_create_inverted_index(table, use_tantivy, with_position):
     if use_tantivy and not with_position:
         pytest.skip("we don't support building a tantivy index without position")
-    table.create_fts_index("text", use_tantivy=use_tantivy, with_position=with_position)
+    table.create_fts_index(
+        "text",
+        use_tantivy=use_tantivy,
+        with_position=with_position,
+        name="custom_fts_index",
+    )
+    if not use_tantivy:
+        indices = table.list_indices()
+        fts_indices = [i for i in indices if i.index_type == "FTS"]
+        assert any(i.name == "custom_fts_index" for i in fts_indices)
 
 
 def test_populate_index(tmp_path, table):