[clang] Disable a few formatting options for test/

Hopefully this will make the bot a little less noisy. Rationale for each:

AlignTrailingComments: We don't want to force-align the various expected-error
                       and friends.

CommentPragmas:       Tell clang-format to leave the "// CHECK:" and the
                      "// expected-" alone.

AlwaysBreakTemplateDeclarations: Templates in tests often have no break between
                                 the template-head and the declaration.

Differential Revision: https://reviews.llvm.org/D83901