Improve automated archiving workflow

[e-belfer]

We've made a series of improvements to our automated archiving infrastructure (#418, #372, #357, #346, etc.).

This epic collects a suite of issues and tasks related to improvement of the automation of archiving, based on regular review of the auto-created issues.

• If automated archiver run produces all "no changes", don't auto-create Github issue #898
• When runs timeout, they don't show up in the run summary/issue at all: Add timed-out runs to monthly automated archiving #968
• Replace <br> symbols with actually rendered spaces and add task-list items Render auto-created github issues using markdown, auto-add task lists #1061
• When failed archives are re-run from GHA, they should either overwrite or comment on the originally posted issue. Right now we create a new issue with a concatenation of both runs' summaries, meaning that if a run failed and then later succeeded it shows up twice in two different states in the Github issue.