[8.x] Add setKeysForSelectQuery method and use it when refreshing model data

[adamthehutt]

This PR is in reference to #34954.

It adds two methods to the base Model class: setKeysForSelectQuery() and getKeyForSelectQuery(). These methods are then used in fresh() and refresh() instead of the existing setKeysForSaveQuery() and getKeyForSaveQuery().

[GrahamCampbell]

Thanks for the PR. Isn't this a breaking change?

[adamthehutt]

@GrahamCampbell I don't think it is, no. This just addresses a change that was made in #34836. Prior to that, the setKeysForSelectQuery() method was not being called on fresh() or refresh(). That was (for me, anyway) a breaking change. And it seemed semantically incorrect, since refresh() and fresh() are not save queries. @driesvints and @taylorotwell seemed to agree in thread #34954.

[driesvints]

I think this looks okay but will need @taylorotwell to verify it.

[axlon]

@GrahamCampbell @adamthehutt @driesvints This is indeed a BC, because this breaks refresh and fresh on pivots and morphpivots again (which my original PR intended to fix). I just composer updated and have tests that are suddenly failing.

The error:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'id' in 'where clause' (SQL: select * from `invites` where `id` is null limit 1)