resolvemerge: Improve cleanup of files that were deleted by one side of a conflicted...

resolvemerge: Improve cleanup of files that were deleted by one side of a conflicted merge, and modified by the other side

This case was handled by cleanConflictCruft, but only when the annexed
file's object was present. When not present, it left the annexed file
with the original name, not checked into git, while adding the variant
file. So, add an explicit deletion of the deleted file in this case.

My specific case where this happened actually involves
merge.directoryRenames=conflict. After a merge involving that,
the situation was the file appears as "added by them", because that
caused the file that they added to be moved into a directory we renamed.

That case is the same as them adding a modified version of the file,
while we deleted it. (Except for the history of the file, since it's a
new file, but this doesn't look at history.)

This commit was sponsored by Boyd Stephen Smith Jr. on Patreon.