perf: directly create projection instead of using DataFrame::with_column

[emcake]

Description

DataFrame::with_column performs a linear operation in the number of columns to append on an existing column, checking that nothing collides. On top of this once the projection a normalization step (also linear in number of columns) is performed before returning the dataframe.

For a merge where we are performing a when_matched_update_all type operation on wide tables (100+ columns), this is in effect a 2*N^2 operation as we were adding the remapped case columns one at a time with with_column and then remapping it.

This PR uses project directly to construct the logical plan. We don't need any of the special checking for name clashes or windowing that with_column provides and we discard it immediately down to an unoptimized logical plan anyway, so this produces no change to schema - just a much more compact logical plan.

This reduces an example merge I had from taking 5+ minutes to just optimize the table, down to about 13 seconds including the merge.

[Blajda]

LGTM! Thanks for looking into the performance issues :)

[ldacey]

Nice - this will be huge. So this should be in the 0.15.4 release then?