Add multi-thread compression for gpfdist in gpdb6

[Hlinbit]

This PR mainly involves synchronizing the main branch with the multithreaded compression transmission functionality for gpfdist external table. It includes the following features:

• compression and decompression of data transmitted to and from gpfdist external tables
• support for multithreaded compression of multithreaded data on readable external tables.

For detailed functionality, refer to the following PRs:

• Compression and decompression of data transfer for readable external tables #14144
• Compression and decompression of data transfer for writable external tables #14250
• Multithreaded compression of the content transferred from readable external tables. #14698