add assertDatabaseHasMany assertion

[bmckay959]

Q	A
Bug fix?	no
New feature?	yes
Fixed tickets	none

Every project I use, I reach for this and realize it's not there, so I end up adding this into my own custom assertions. It's a nicety to not have to make each assertion setup with the table. It just creates a foreach loop over the top of assertDatabaseHas().

Current Way:

assertDatabaseHas('users', [
   'id' => 1
]);

assertDatabaseHas('users', [
   'id' => 2
]);

New Way:

assertDatabaseHasMany('users', [
   ['id' => 1],
   ['id' => 2]
]);