Print diagnostic groups as part of the LLVM printer in the same manner as the
Swift one does, always. Make `-print-diagnostic-groups` an inert option, since we
always print diagnostic group names with the `[#GroupName]` syntax.
As part of this, we no longer render the diagnostic group name as part
of the diagnostic *text*, instead leaving it up to the diagnostic
renderer to handle the category appropriately. Update all of the tests
that were depending on `-print-diagnostic-groups` putting it into the
text to instead use the `{{documentation-file=<file name>}}`
diagnostic verification syntax.
This should have been done for Swift 4.2 according to SE-0204, but
better later than never. Deprecating these methods as of Swift 5.0.
Also modfying the tests to check for the deprecation message.
Fixes: <rdar://problem/43694210>