feat(mock-plugin): moves mock stuff to their own plugin

tests/.snapshots/success.txt

@@ -77,10 +77,6 @@
   ✓ it can call chained macro method
   ✓ it will throw exception from call if no macro exists
 
-   PASS  Tests\Features\Mocks
-  ✓ it can mock methods
-  ✓ it allows access to the underlying mockery mock
-
    PASS  Tests\Features\PendingHigherOrderTests
   ✓ get 'foo' → get 'bar' → expect true → toBeTrue 
   ✓ get 'foo' → expect true → toBeTrue 
@@ -223,5 +219,5 @@
   ✓ it is a test
   ✓ it uses correct parent class
 
-  Tests:  7 skipped, 121 passed
+  Tests:  7 skipped, 119 passed