feat(appcomposer): Update CFN snippet source

[truggeriaws]

Problem

The AppComposer generate feature is moving from a call to the Q extension to a call to our owned CDN, the same CDN that hosts our webview, or CFN template partials.

Solution

This PR updates the code that used to make a call to the Q extension and instead replaces it with fetch call to the CDN to gather data. Error cases (such as the requested file not being found or the CDN being down) are handled by the existing code.

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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
  • Confirm whether tests should be added or ensure the PR description explains why tests are not required.
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[bildungsroman]

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