Resolve "Remove usage ping payload from Cohorts, add to Settings"

What does this MR do?

• Remove async usage ping JSON component from user cohorts page
• Allow admins to view the usage ping JSON payload from the admin/application_settings "usage statistics" section
• Remove admin-specific information from convdev index empty state for non-admin users
• Update convdev index empty state copy
• Hide cohorts button when usage ping is disabled
• 404 cohorts page for non-adminusers when usage ping is disabled
• Hide convdev banner when usage ping is disabled
• Updates instance statistics docs so they tell the truth

Screenshots

settings

non-admin

convdev

cohorts

admin

convdev

cohorts

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #50567 (closed)