[clang-format] Add more tests for Objective-C 2.0 generic alignment

Summary:
In r236412, @djasper added a comment:

    // FIXME: We likely want to do this for more combinations of brackets.
    // Verify that it is wanted for ObjC, too.

In D42650, @stephanemoore asked me to confirm this.

This followup to D42650 adds more tests to verify the relative
alignment behavior for Objective-C 2.0 generics passed to functions
and removes the second half of the FIXME comment.

Test Plan:
  make -j12 FormatTests && \
  ./tools/clang/unittests/Format/FormatTests --gtest_filter=FormatTestObjC.\*

Reviewers: stephanemoore, jolesiak, djasper

Reviewed By: jolesiak

Subscribers: klimek, cfe-commits, djasper, stephanemoore, krasimir

Differential Revision: https://reviews.llvm.org/D42864

llvm-svn: 324364