[lldb][NFC] Refactor printing of short options in help
Instead of building a set twice for optional and required,
build a set for each while walking the options once.
Then take advantage of set being sorted meaning we don't
have to enforce the upper/lower order ourselves.
Just cleaned up the formatting on the later loops.
Combined the if conditions and used a single line if.
Depends on D123501
Reviewed By: jingham
Differential Revision: https://reviews.llvm.org/D123502
