fix(deletion_vector): read Java bitmap64 deletion vectors

[jackylee-ch]

A deletion vector written by Java in the 64-bit format (Bitmap64DeletionVector)
cannot be read: read_from_bytes accepts only the v1 magic, so every scan touching
such a file fails with Invalid magic number, naming the v1 magic alone.
Java's DeletionVector.read dispatches on both.

Two things differ beyond the value. The v2 magic is written little-endian, and
DeletionFile.length() counts the length prefix and the CRC for v2 but neither for
v1. The second also breaks the read range: the factory asks for length + 8, past
the end of a v2 entry, so a vector ending its index file is rejected by the storage
layer before parsing.

Fix: detect either magic, apply each format's length convention, and decode
the payload as portable 64-bit roaring. Java run-length encodes before writing and
emits every bucket key densely, so tests cover both shapes.

Read side only; the writer still emits v1. Positions above u32::MAX are rejected
rather than truncated — every API here is already roaring32-bound, and reaching
one needs a data file with over 4.29e9 rows. A negative bitmapLength read from
the file now errors instead of wrapping the size guard into passing.