Add support for bitmap construct agg

### Description

Register bitmap_construct_agg as a supported aggregate expression in the Velox backend, allowing it to be executed natively instead of falling back to vanilla Spark.

### Gluten version

Gluten-1.6

The issue names the Velox backend and the bitmap_construct_agg expression but no files or tests. Start by searching the repository for supported aggregate expressions and existing bitmap aggregate registrations. Done means bitmap_construct_agg is registered for native execution and relevant backend tests pass without falling back to vanilla Spark.

Written by the indexing model from the issue text.