ARROW-11738: [Rust][DataFusion] Fix Concat and Trim Functions

[seddonm1]

This PR is a child of #9243

It does a few things that are hard to separate:

• fixes the behavior of concat and trim functions to be in line with the Postgres implementations
• restructures some of the code base (mainly sorting and adding tests) to facilitate easier testing and implementation of the remainder of ARROW-11298: [Rust][DataFusion] Implement Postgres String Functions [Splitting to separate PRs] #9243

@alamb@jorgecarleitao
please review but merging will be dependent on #9507

[github-actions]

https://issues.apache.org/jira/browse/ARROW-11738

[alamb]

Thanks @seddonm1 -- I will plan to review this over the next few days

[seddonm1]

@Dandandan I can add substr to this PR if that would help you with TCPH-q22?

[seddonm1]

@Dandandan I have added substr to this PR

[Dandandan]

Alphabetically, this should be after concat?

[seddonm1]

yes, my VSCode sorting treats _ before ". fixed 👍

[Dandandan]

LGTM!
I think from time to time we will can check on the status of the tpch queries. Feel free to split the PRs in the way you think makes sense @seddonm1 👍

[seddonm1]

LGTM!
I think from time to time we will can check on the status of the tpch queries. Feel free to split the PRs in the way you think makes sense @seddonm1 👍

@Dandandan basically the string functions PR is so big even splitting like this makes a big difference and allows applying some of the foundational components (see the testing) required for the rest. So if this helps unblock you then thats a good thing :D

[alamb]

Epic work @seddonm1 -- thank you again. I skimmed this and spot checked a few functions, but it all looks as good as #9243 is. I think this one is good to merge.

[alamb]

This PR sadly does need a rebase

[seddonm1]

thanks @alamb rebased 👍

[alamb]

Integration test failure looks like https://issues.apache.org/jira/browse/ARROW-11717, so ignoring