debugindex: add a `p1-rev` column This will be useful in case of corrupted index.

debugindex: introduce a concept of "verbose-only" column We are about to add a bunch of new column and most of them are probably only relevant to --verbose. We add some more testing of the `--verbose` mode in a sidedata context.

debugindex: move to a flexible column Each column is now declared as a decorated function. This will make it much simpler to add more new column in the future.

debugindex: rename the parent column to mention nodeid We will add new columns with the "revnum" version of the parent. It will be useful in case we need to inspect a corrupted revlog index.

debugindex: align column name on the right It will be simpler to align everything on the same side, and the right seems a better side as it match the value alignment.

debugindex: move the logic into its own module Adding more information will significantly increase the amount of code. So we move the code into its own module before making it more complex.