[monodroid] Enable a number of tests (#5799)
Just over a year ago Xamarin.Android switched to running BCL tests straight
from the Mono sources but at the time we decided we didn't want to enable
a number of "new" tests (in the sense - never previously ran on XA) to avoid
introducing new failures in time which required focusing on more important
goals.
Currently, Xamarin.Android no longer uses Mono **sources** to build its tests
but, rather, it uses test **assemblies** built by Mono. This commit restores
the previously excluded tests in preparation for full BCL test coverage in
the near future.
14 files changed: