Linter/DocumentationLinks: Flag help links with receivers

What does this MR do and why?

This MR fixes the HAML linter rule Linter/DocumentationLinks to flag the invalid use of page links with receivers.

Now, the following examples are matched:

= Rails.application.routes.url_helpers.help_page_path("invalid/path")
= Gitlab::Routing.url_helpers.help_page_path("invalid/path")
= Actually::Anything::NotGonnaLie.help_page_path("invalid/path")

It also improves the speed of the rule by caching the compilation of the node pattern 🚀

For example, this improves the runtime for haml-lint app/views/shared by 2.5s (19s -> 16.5s) 🎉

This MR also fixes the sole offense in ee/app/views/shared/issuable/form/_merge_request_blocks.html.haml.

How to set up and validate locally

Before

$ bundle exec haml-lint  ee/app/views/shared/issuable/form/_merge_request_blocks.html.haml
ee/app/views/shared/issuable/form/_merge_request_blocks.html.haml:15 [W] DocumentationLinks: help_page_path points to the unknown location: /home/peter/devel/gitlab/gdk/gitlab/doc/user/project/merge_requests/dependencies.html.md

1 file inspected, 1 lint detected

See https://gitlab.com/gitlab-org/gitlab/-/jobs/3709855812

After

$ bundle exec haml-lint  ee/app/views/shared/issuable/form/_merge_request_blocks.html.haml

1 file inspected, 0 lints detected

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.