Allow admins to have a scanner-held version auto-approved without explicit removal.

[wagnerand]

(MVP of #7288).

When auto-approval is held-back for a version because of a security scanner rule action, admins would need a way to manually have that version auto-approved.

(The only way to approve currently is using the reviewer tools. This is undesirable because it indicates the version has been reviewed and follows the add-on policies, which is not necessarily the case).

[diox]

I think we want two three things here:

• Moving the scanners to only delay auto-approval of the version they have scanned, not the entire add-on. Maybe create a new model to hold reviewer-specific flags for versions (and not add-ons as we already have) and create the field there. Bonus points: also move needs_human_review while we're at it
• Adding a button somewhere to remove that delay
• A one time migration to "fix" add-ons that have been delayed indefinitely because of a false-positive (removing the delay for them) and to move the delay to the version only for the rest.

[wagnerand]

@diox pointed out that we already have a way to do this. Let's close this for now and revisit later if needed.