feat(scanner): add external row-address mask prefilter

[JulianYG]

Addresses #6852.

What

Adds Scanner::with_row_addr_prefilter(RowAddrMask), letting callers pass a
precomputed row-address allow/block mask as a prefilter into vector and plain
scans, reusing the scanner's existing retrieval plan rather than re-deriving it.

Motivation

Some pipelines precompute a set of eligible rows out-of-band (e.g. a stored
bitmap of rows belonging to a logical subset / dataset) and want to run KNN or a
plain scan restricted to that set -- without expressing it as a SQL filter. A
multi-hundred-thousand-element IN (...) is impractical to build and parse;
passing the row set directly is far cheaper.

How

The mask threads into the existing prefilter machinery at three points:

• ANN branch: fed through PreFilterSource into new_knn_exec, ANDed with
  any deletion/SQL prefilter via a MaskAndLoader.
• Flat / unindexed-fragment branch: a new RowAddrMaskFilterExec filters
  scan output by _rowid, so rows appended after the index build are honored.
• Plain (non-vector) scan: the mask is supplied as the FilteredReadExec
  index input, so only masked rows are read; a SQL filter becomes a refine on top.

Deletions are still applied by DatasetPreFilter; illegal addresses are ignored.

Status

Draft, pending API agreement on #6852. Behavior is exercised by an out-of-tree
PyO3 binding's test suite (based on v7.0.0, this PR is rebased); cargo check -p lance and cargo fmt are clean. I'd
appreciate guidance on the public API shape before finalizing in-tree tests.