Expand and document PSRT coordination process

[sethmlarson]

This PR defining the coordination process more concretely. Here are the changes:

• Changes the process to automatically assign a Coordinator after a period of idleness. The exact selection process isn't defined, at this stage I am looking for reviews on whether this change to the process is acceptable to PSRT members.
• The coordinator role per-ticket is explicit within GHSA using the "Credit: Coordinator" feature.
• Separates the Triage, Remediation, Advisory sub-processes more clearly. This intended to be helpful for non-PSRT members that are involved in the remediation process to know what to expect.
• Documents how the PSRT bot operates so coordinators know what to expect and how to take advantage of the automation.

cc @python/psrt

[read-the-docs-community]

Documentation build overview

📚 CPython devguide | 🛠️ Build #31903351 | 📁 Comparing 7ac2889 against latest (7a807eb)

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Show files changed (12 files in total): 📝 10 modified | ➕ 2 added | ➖ 0 deleted

File	Status
index.html	📝 modified
_static/psrt-coordinator-report.html	➕ added
_static/psrt-coordinator-triage.html	➕ added
core-team/index.html	📝 modified
developer-workflow/index.html	📝 modified
testing/index.html	📝 modified
versions/index.html	📝 modified
core-team/experts/index.html	📝 modified
developer-workflow/psrt/index.html	📝 modified
development-tools/clinic/index.html	📝 modified
documentation/style-guide/index.html	📝 modified
testing/new-buildbot-worker/index.html	📝 modified