Refactor new help formatting implementation
- Merge formatFileOption() and formatOption() into one.
- Remove unnecessary generality by splitting description formatting into
its own class, and make OptionsFilter only do option filtering. All
output handling is now in OptionsListFormatter (which was renamed from
OptionsExportFormatter).
- Split formatting basic option name and value placeholders into a
separate function.
There should be no functional change. Preparation for a proper synopsis
implementation.
Part of #969.
Change-Id: I900883eb39853ed67d5f6177ae06847283348d9e