Support Blind APPENDs via the Kernel so we can flush Parquet using Native C# rather than Arrow FFI pointers

[mdrakiburrahman]

Kernel now supports writes:
https://github.com/delta-io/delta-kernel-rs/blob/main/kernel/tests/write.rs

Extend the interface to add it.

Also, if possible, support writing Parquet out of the Rust Proc (as native Dotnet, say, https://github.com/aloneguid/parquet-dotnet), and only have Kernel write the metadata.

(We could consider whether we want to add Parquet Dotnet as a dep in this project).

[mdrakiburrahman]

@mightyshazam - I'll grab this guy after coming back from vacation (new years).

[flambert860]

Hey @mdrakiburrahman , any updates on this? :)