Port xplr.fn.builtin.fmt_general_table_row_cols_* over to Rust

[sayanarijit]

Similar to https://github.com/sayanarijit/xplr/issues/644, but for xplr.fn.builtin.fmt_general_table_row_cols_*

See

https://github.com/sayanarijit/xplr/blob/f3a2d519b12346084f044148c4e62918c3951c30/src/init.lua#L183

Let's make it nullable, and default to null.

Also, the following functions should be gone.

https://github.com/sayanarijit/xplr/blob/f3a2d519b12346084f044148c4e62918c3951c30/src/init.lua#L2944 https://github.com/sayanarijit/xplr/blob/f3a2d519b12346084f044148c4e62918c3951c30/src/init.lua#L2983 https://github.com/sayanarijit/xplr/blob/f3a2d519b12346084f044148c4e62918c3951c30/src/init.lua#L3004 https://github.com/sayanarijit/xplr/blob/f3a2d519b12346084f044148c4e62918c3951c30/src/init.lua#L3013

Opinion/discussion: We should probably have a single column by default.

Subtask of https://github.com/sayanarijit/xplr/issues/641