Fetch template icons

[amrit110]

This pull request adds support for displaying template icons in the templates table of the analytics dashboard. The changes include updating the backend to provide the icon URL, updating type definitions, enhancing the table UI to render the icon, and configuring Next.js to allow images from specific remote sources.

Backend and Data Model Updates:

• The compute_template_metrics function in coder/analytics/aggregate.py now includes a template_icon field in its output, sourcing the icon URL from the template if available.
• The TemplateMetrics TypeScript interface in services/analytics/lib/types.ts is updated to include a new template_icon property.

Frontend/UI Enhancements:

• The TemplatesTable component in services/analytics/app/components/templates-table.tsx is updated to display the template icon (if present) using the Next.js Image component. If no icon is provided, a default icon is shown.
• The Image component from Next.js is imported to support optimized image rendering.

Configuration:

• The Next.js config in services/analytics/next.config.js is updated to allow loading images from cdn-icons-png.flaticon.com, enabling the use of remote template icons.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.62%. Comparing base (8c3b6a4) to head (1029173).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #80   +/-   ##
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  Coverage   90.62%   90.62%           
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  Files          10       10           
  Lines        1408     1408           
=======================================
  Hits         1276     1276           
  Misses        132      132           

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