fix: upsert with composite unique index

[michalsn]

Description
This PR fixes a bug in Postgre and SQLite3 where composite indexes are not fully taken into account when using upsert().

Both handlers:

• requires specifying all columns in the composite unique constraint
• and cannot mix columns from multiple unique constraints

Fixes #9450

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[sclubricants]

Posgre has very different functioning then MySQL when it comes to upserts. Postgre offers much more features while mysql automatically applies any and all constraints. It was attempted apply the primary key if constraints were not set. Its really just a guess but it was done to try and provide the same functionality across all databases. For all the DBMS except mysql it is really recommended to use the onConstraint() method and explicitly define them. Perhaps the documentation should highlight this.

[michalsn]

While I agree that onConstraint() should be used when dealing with multiple keys, in cases where we have one composite key, it should be automatically applied as a whole and not partially.

[michalsn]

Thank you @paulbalandan and @samsonasik