No way to select Standard post format in Formats filter

[SergeyBiryukov]

Background: #35497, #46591, #47359.

[45136] removed post format icons from the posts list table.

For some users, as noted in comment:52:ticket:35497, these icons were a convenient way to quickly distinguish posts with a format from standard posts.

Use case: when most of the posts have a non-standard format, you'd like check if there are any posts where you accidentally forgot to assign a format.

Even with the new Formats filter introduced in [44961], that's no longer possible, as it does not have a Standard option. This seems a bit inconsistent with the Categories filter, where you can filter by Uncategorized.

Brought up by @dimalash on support forums.