Since !18150 abstract reference filter supports also `group`
as a resource parent (not only `project`). Some reference filters,
which inherit from abstract filter, depend on parent being `project`
when checking a reference.

This patch adds explicit check of parent class to the given filters.

This refactors the Markdown pipeline so it supports the rendering of
multiple documents that may belong to different projects. An example of
where this happens is when displaying the event feed of a group. In this
case we retrieve events for all projects in the group. Previously we
would group events per project and render these chunks separately, but
this would result in many SQL queries being executed. By extending the
Markdown pipeline to support this out of the box we can drastically
reduce the number of SQL queries.

To achieve this we introduce a new object to the pipeline:
Banzai::RenderContext. This object simply wraps two other objects: an
optional Project instance, and an optional User instance. On its own
this wouldn't be very helpful, but a RenderContext can also be used to
associate HTML documents with specific Project instances. This work is
done in Banzai::ObjectRenderer and allows us to reuse as many queries
(and results) as possible.

Updates notes-related services and rendering so this code can be
easily used for group-scoped resources (specifically Epics).

Related to gitlab-ee!5205

We displayed the correct text as the link text (without double-encoding), but
didn't do the same for the actual link target, so any link containing an
ampersand would break when auto-linked.

Now the issuable reference check works only in project scope, if we
reference an issuable from a non-project resource (e.g. epics), then
project is not set, and there is mismatch in generated issue references.

This patch enables issuable reference state check also from group scope.

Closes gitlab-ee#4683
Related to #30916

Rinku 2.0.0 (the version we use) will remove the last character of a link if
it's a closing part of a punctuation pair (different types of parentheses and
quotes), unless both of the below are true:

1. The matching pair has different start and end characters.
2. There are equal numbers of both in the matched string (they don't have to be
   balanced).

Since the redactor can be run on multiple documents at once and
query results are stored in the request store.

[10.4] Fix stored XSS in code blocks

There are certain inputs that look like valid URIs that are accepted by URI
but not Addressable::URI. Handle the case where the latter fails.

Closes #41442

TableOfContents filter generates hrefs for each header in markdown,
if the header text consists from digits and redacted symbols only,
e.g. "123" or "1.0 then the auto-generated href has the same format
as issue references.

If the generated id contains only digits, then 'anchor-' prefix is
prepended to the id.

Closes #38473