add --skip-information flag to clean cmd for consistency

[developer-guy]

Description

Based on the talk in Slack¹ with @imjasonh, it'd be better for consistency to use the skip-information flag for clean cmd in addition to the force flag.

The whole UX would be like the following:

1. We'll probably want --force to continue to exist for 1+ release, with a warning that it's renamed to --skip-confirmation.
2. use --force's value to set o.SkipConfirmation.
3. If both are set and they disagree, then fail.

Footnotes

1. https://github.com/sigstore/cosign/pull/2039#discussion_r911985088 ↩

[developer-guy]

@dentraz would you like to give this one a hand?

[znewman01]

CC @haydentherapper; see also #1909 and my comments therein

Before a rename I'd really like to see some documentation (comments in the code would be sufficient) about our prompting philosophy first. I think it's really useful to have (1) consistent principles for flag naming, prompting, etc. across the tool and (2) communicate those to users, so they know what to expect.

I also prefer --force as a flag name because I don't want bespoke flags per each acknowledgment but I wouldn't put up a fight about it.

[znewman01]

Also I think you wanted @Dentrax :)