Remove angular waltz-markdown, replace with svelte based control

[davidwatkins73]

Description

Currently have two slightly different version of markdown support.

• ng-showdown
  • last commit > 4yrs ago. Some dependencies being flagged for vulns.
• raw showdown wrapped in basic svelte control

This issue proposes to remedy that by standardizing on the newer svelte wrapper control

Resourcing

We intend to implement this task

[davidwatkins73]

Looks like about 60 angular controls may be impacted by this change (prob. 2 files per control = 120 files impacted)

[davidwatkins73]

May be easier to make the waltz-markdown angular control wrap the svelte component (using waltz-svelte-component) and then gradually phase out.