[ELF] Add alias options for start-group/end-group options.

There are aliases for --start-group/--end-group options represented
by -( and -) respectively in the command line.

This change adds and improves the test for the alias options to be
tested.

Looks like users use this option widely than explicitly using
--start-group/--end-group.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@192470 91177308-0d34-0410-b5e6-96231b3b80d8