test: move background index build test to engine suite from vinyl

Since we have implemented memtx background index build, the
corresponding vinyl test cases are now also suitable for memtx,
so move them to engine suite so that both engines are tested.
Also add some tests to check that an ongoing index build is aborted in
case a tuple violating unique constraint or format of the new index is
inserted.
Add some error injections to unify appropriate memtx/vinyl tests.

Closes #3976