Revlog index data consists of generic index metadata that will
likely be implemented across all storage engines and revlog-specifc
Most tests printing index data only care about the generic fields.
This commit drops the printing of the base revision from
hg debugindex. This value is an implementation detail of
revlogs / delta chains. If tests are interested in verifying this
implementation detail, hg debugdeltachain is a better command.
Most tests were skipping over this field anyway. Tests that weren't
looked like they were newer. So my guess is we forgot to make them
skip the field to match the style of the older tests. This reinforces
my belief that the base revision is not worth having in