Preload project features in reference parser

Closes #43094

See merge request gitlab-org/gitlab-ce!22008

Changes `Banzai::CrossProjectReference#parent_from_ref` to return the
project in the context if the project's `full_path` matches the ref
we're looking for, as it makes no sense to go to the database to find a
Project we already have loaded.

Preloading of project_features mitigates N+1 queries when checking
references in other projects.

When loading projects for resources referenced in comments it
makes sense to include also associated project_features because
in the following step (`can_read_reference?(user, projects[node],
node)`) project features is used for checking permissions for the given
project.

https://gitlab.com/gitlab-org/gitlab-ce/issues/52009

Even if it doesn’t save lines of code, since people will tend to use
code they’ve seen. And `SafeRequestStore` is safer since you
don’t have to remember to check `RequestStore.active?`.

Resolve "Markdown footnotes don't render when inside a table..."

Closes #51200

See merge request gitlab-org/gitlab-ce!21675

- utilize the 'out' method to output the 'fence_info',
  which converts to utf8
- output 'sourcepos' again