[Task]: Implement soften and harden block actions in the admin

[diox]

Description

Follow-up from #15013

The admin should support a way to directly change a hard-blocked version to being soft-blocked and vice-versa, with full logging/confirmation like other blocklisting actions.

Acceptance Criteria

Milestones/checkpoints

Beta Give feedback

1. Blocks can be "hardened" in the admin
2. Blocks can be "softened" in the admin

Checks

• If I have identified that the work is specific to a repository, I have removed "repository:addons-server" or "repository:addons-frontend"

┆Issue is synchronized with this Jira Task

[diox]

mozilla/addons-server#22827 has some screenshots of the new UI bits. There are notably new harden/soften buttons when you're viewing a block. It should require the same permissions as for creating a block (Blocklist:Create) and the same sign-off as normal if that's a high adu (> 100k) add-on.

All the changes to the blocklist itself haven't landed, but you should be able to view the changes in the admin once processed. A hard blocked version can be softened to a soft-block, a soft-blocked version can be hardened to a hard-block.