Ensure that rendered views has no HTML escaped tags

What does this MR do and why?

This MR adds a shared context which ensures in each view spec example that rendered does not contain any HTML escapes.

This shared context is run for every view spec (via RSpec's type: :view metadata).

This is to catch cases where we forget to use .html_safe.

This check can be disabled via :skip_html_escaped_tags_check in cases where it is explicitly tested whether HTML tags are escaped.

Example failure message

Failures:

  1) notify/approved_merge_request_email.html.haml contains approval information
     Failure/Error:
           raise <<~MESSAGE
             The following string contains HTML escaped tags:

             #{string}

             Please consider using `.html_safe`.

             This check can be disabled via:

               it #{example.description.inspect}, match_html_escaped_tags: false do

     RuntimeError:
       The following string contains HTML escaped tags:

       yle="height:18px;width:18px;margin-bottom:-4px;">
       «&lt;span» style=&quot;font-weight: 600;color:#333333;&quot;

       Please consider using `.html_safe`.

       This check can be disabled via:

         it "contains approval information", :skip_html_escaped_tags_check do
           ...
         end

Out of scope

This MR does not verify the rendered email content contains escaped HTML tags. However, some mailers use views to render emails.

Verify locally

• Revert !96548 (merged) via git revert -m 1 8fba8900
• Run specs via bin/rspec spec/views/notify/approved_merge_request_email.html.haml_spec.rb
• See failure from above

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.