Scan Delete Support Part 2: introduce DeleteFileManager skeleton. Use in ArrowReader

[sdd]

Second part of delete file read support. See #630.

This PR provides the basis for delete file support within ArrowReader.

DeleteFileManager is introduced, in skeleton form. Full implementation of its behaviour will be submitted in follow-up PRs.

DeleteFileManager is responsible for loading and parsing positional and equality delete files from FileIO. Once delete files for a task have been loaded and parsed, ArrowReader::process_file_scan_task uses the resulting DeleteFileManager in two places:

• DeleteFileManager::get_positional_delete_indexes_for_data_file is passed a data file path and will return an Option<Vec<usize>> Option<RoaringTreeMap> containing the indices of all rows that are positionally deleted in that data file (or None if there are none)
• DeleteFileManager::build_delete_predicate is invoked with the schema from the file scan task. It will return an Option<BoundPredicate> representing the filter predicate derived from all of the applicable equality deletes being transformed into predicates, logically joined into a single predicate and then bound to the schema (or None if there are no applicable equality deletes)

This PR integrates the skeleton of the DeleteFileManager into ArrowReader::process_file_scan_task, extending the RowFilter and RowSelection logic to take into account any RowFilter that results from equality deletes and any RowSelection that results from positional deletes.

Updates:

• refactored DeleteFileManager so that get_positional_delete_indexes_for_data_file returns a RoaringTreemap rather than a Vec<usize>. This was based on @liurenjie1024's recommendation in a comment on the v1 PR, and makes a lot of sense from a performance perspective and made it easier to implement ArrowReader::build_deletes_row_selection in the follow-up PR to this one, Scan Delete Support Part 3: ArrowReader::build_deletes_row_selection implementation #951

Potential further enhancements:

• Instantiate and store the DeleteFileManager in the ArrowReader rather than per-task so that delete files that apply to more than one task don't end up getting loaded and parsed twice
• Go one step further and move loading of delete files, and parsing of positional delete files, into ObjectCache to ensure that loading and parsing of the same files persists across scans

[sdd]

@liurenjie1024, @Xuanwo, @Fokko - this is ready for review when any of you get chance. Thanks! :-)