debugcommands: drop offset and length from debugindex by default
These fields are an implementation detail of revlog storage. As
such, they are not part of the generic storage "index" interface
and shouldn't be displayed by default.
Because we don't have another way to display these fields, we've
retained support for printing these fields via --verbose.
Yes, I know we should probably be doing all this formatting using
modern formatting/templater APIs. I didn't feel like scope
bloating this patch.
Differential Revision: https://phab.mercurial-scm.org/D3028