feat: converts batches in old format to the flat format in query time

[evenyag]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

#6078

What's changed and what's your intention?

This PR converts batches to flat format when reading files with the old format.

• FlatReadFormat will check whether it needs to convert the format
• Refactor ReadFormat::new to receive num_columns and file_path for FlatReadFormat
• FlatFormat now uses an enum ParquetAdapter to get stats and compute projection for the parquet file.
• ParquetAdapter will delegate the operation to PrimaryKeyReadFormat if the file has the old format.
• Support sparse encoding in flat format (BulkMemtable will also convert the flat format)

Other minor fixes:

• Only uses dictionary type for strings in compute_input_arrow_schema()
• Avoid adding the same file to the file cache index twice

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[fengjiachun]

LGTM