[9.x] Add "incrementEach" to the Query\Builder

[imanghafoori1]

This is useful when the user wants to atomically increment multiple columns by a single query.
For example, subtract from wallet1 and add the same amount to wallet2 in order to transfer money.

DB::table('users')->where('id', 2)->incrementColumns([
     'wallet_1' => -30,
     'wallet_2' => 30,
], ['updated_at' => now()]);

or keep a proper update of pre-calculated columns:

DB::table('products')->where('id', 2)->incrementColumns([
     'in_store' => 2,
     'in_stock' => 3,
     'total' => 5,
], ['updated_at' => now()]);

• The logic can be reused in increment to avoid code duplication.
• The method is named incrementColumns to indicate that it "increments many columns" (not sure if it is the best name).
• A comprehensive set of integration tests is included. Since the increment now uses incrementColumns the tests also cover it as well, plus some unit tests

[taylorotwell]

Renamed to incrementEach.