Sanitize slack-formatted links in chat messages

What does this MR do and why?

This sanitizes text matching the link format for a slack message from issue descriptions.

The slack link format is <http://custom-url.com|CLICK HERE>

The change here uses a regex to match relevant strings then escape the < and > characters with < and > respectively.

This renders the text as written and doesn't convert it to a link.

Changelog: other

Screenshots or screen recordings

Before

After

How to set up and validate locally

This is complicated to do as it requires starting a gitpod instance and connecting it to our Slack (Dev) instance.

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.

Related to #387837 (closed)