Using mock-apollo-provider results in a more realistic test, since the
internals of the component(s) (i.e., `data`) aren't manipulated by the
test suite.

This change also removed an unnecessary use of `localVue` in a related
test suite, and moved the SAST spec helpers up a level in the tree.

Addresses https://gitlab.com/gitlab-org/gitlab/-/issues/249556.