Change dynamic MIME tests according to API changes

PackageManager#clearMimeGroup was removed. This CL modifies test to use
PackageManager#setMimeGroup instead, removes test cases that are no
longer relevant and reflects that get/set methods on undefined MIME
groups should throw.

Bug: 151101912
Test: atest CtsDynamicMimeHostTestCases
Change-Id: I0af773523c84ac5aeccfcba3851da5fb36607b0e