Allow external diffs to be used conditionally

Closes #54670

See merge request gitlab-org/gitlab-ce!25432

Since external diffs are likely to be a bit slower than in-database
ones, add a mode that makes diffs external after they've been obsoleted
by events. This should strike a balance between performance and disk
space.

A background cron drives the majority of migrations, since diffs become
outdated through user actions.

Adds the groundwork needed in order to persist multi-line suggestions,
while providing the parsing strategy which will be reused for the
**Preview** as well.

Adds outdated, lines_above and lines_below columns to
suggestions table.

outdated - boolean which represents whether the suggestion
is outdated or not. For instance, if any line changed after
you left the multi-line suggestion, even though the note
is not outdated, it helps tracking if the content has changed
in the latest file. We cache this information in a column given
it's not a cheap operation to do for every suggestion in the
request time.
lines_below, lines_above - persists the parsed arguments from
`suggestion:-10+3` syntax, where `10` would be lines_above and
3 lines_below. We need that to dynamically calculate which
lines we should monitor for outdating / persisting the correct
content in from_content column.

This will be further required for supporting multi-assignees MRs

- Includes instance methods on Group model to detect when a group has
AutoDevOps explicitly/implicitly enabled/disabled.
- Includes migration to add a new column to namespaces table
- Add UI necessary modifications
- Add service and controller to update auto devops
related instances
- Updates project and groups auto devops badges

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52447

This reverts commit c9ecc71ab91b0b55f9aba632f9e7b305191a458c, reversing
changes made to c3c8dbf8fa4090bb090071d320a31857eb709d3d.

This makes code to support encrypted runner tokens.
This code also finished previously started encryption
process.