Allow using general compression like zstd for compressing string and binary type of data

[niyue]

Currently, Lance v2 uses FSST to encode string and binary data types when possible. However, compared to general compression methods like zstd, FSST may result in a lower compression ratio and may use significantly more disk space for certain types of strings. Lance v2 does allow users to specify field metadata lance:compression to request general compression, but the current implementation still attempts to apply FSST, even when the user explicitly requests another compression method.

I might be missing something, but it would be ideal if we could honor the user’s explicit choice for general compression in these cases, allowing them to bypass FSST and use the specified compression method. Thanks!