[Ref][Import] Start adding testing to validation, simplify

[eileenmcnaughton]

Overview

[Ref][Import] Start adding testing to validation, simplify

This PR should result in the Preview process continuing to identify if name fields are missing with no change in behaviour

Before

• no testing on the validation process
• validation process follows a very confusing process whereby first it iterates through the fields & determines the 'index' for key fields and then checks that index in the $values array - which represents a row in the csv
• second round of validation for required fields in the deprecated function - which originated from shared code

After

• test
• validation process acts on the $params once the $values row has been mapped to a $params - this means it can just check the params keys
• second round of validation removed

Technical Details

This will be simplified once other open PRs - #23401 #23408 are merged

The second round of validation would have been required in the past for the related contacts (not currently checked in the first round) because it used to then call the Contact:create BAO directly - which didn't do validation. However, it now calls the v3 api - so the same exception would be thrown from the api as would be thrown from the second-round-validation

Comments

Anything else you would like the reviewer to note

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).