[5.8] Fix qualified UPDATED_AT timestamps

[staudenmeir]

#26031 qualified UPDATED_AT timestamps to fix ambiguity issues.

This doesn't work properly when the attributes already contain an updated_at value:

User::first()->update(['name' => 'foo']);

In this case, Builder::addUpdatedAtColumn() returns an array with two separate updated_at values:

array:3 [▼
  "users.updated_at" => "2018-12-30 16:01:40"
  "name" => "foo"
  "updated_at" => "2018-12-30 16:01:40"
]

We have to merge the attributes first and then qualify the column by replacing the array key.

Fixes #26995.

[rennokki]

ETA for the next patch?

[mfn]

Hmm, what for? This went straight into 5.8 which is already released?

[rennokki]

My bad. I feel so stupid for not seeing that the PR got published in December 2018. So the MongoDB issues should be fixed within the MongoDB package.