EE - Improve slash command stripping, escape temporary note contents

What does this MR do?

This MR is an EE port of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11341

Fixes two bugs around Instant comments that were introduced in %9.2 with https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10760

• Comment contents shown as temporary note is vulnerable to XSS (writing <script>alert('Boom!');</script> is not escaped).

• Slash command stripping should also include parameters provided to slash command.

Why was this MR needed?

This MR fixes regression around Instant comments feature as mentioned above.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• [ ] Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/32016

marked the checklist item Added for this feature/bug as completed

marked the checklist item Conform by the merge request performance guides as completed

marked the checklist item Conform by the style guides as completed

marked the checklist item Branch has no merge conflicts with master (if it does - rebase it please) as completed

marked the checklist item Squashed related commits together as completed

changed milestone to %9.2

added 10 commits

• 31d11a12...b305027d - 8 commits from branch master
• 859d9804 - Improve slash command stripping, escape temporary note contents
• c0c340c1 - Update tests for slash commands

Compare with previous version

approved this merge request

enabled an automatic merge when the pipeline for c0c340c1 succeeds

merged

mentioned in commit fdbf646d

mentioned in commit 3e779d18

Picked into 9-2-stable-ee, will go into 9.2.0-rc5-ee.