fix(cloudformation): load stacks lazily to avoid error notification o…

[Zee2413]

…n startup

Problem

New CloudFormation feature eagerly loaded stacks resulting in error notification if credentials were not set properly. Eager loading is not desirable even if credentials would work because user may not open the panel or intend to use the data.

Solution

Lazy load stacks.
Tested:

• stacks do not load on startup
• switching regions does not eagerly load stacks
• pagination with load more works as before
• deploying template if stacks were never loaded triggers loading as stacks are refreshed (desired behavior)
• if StacksNode is expanded and region is switched then stacks are loaded (desired behavior)

Dead code removal: polling was disabled earlier and unused.

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[amazon-inspector-ohio]

⏳ I'm reviewing this pull request for security vulnerabilities and code quality issues. I'll provide an update when I'm done

[github-actions]

• This pull request implements a feat or fix, so it must include a changelog entry (unless the fix is for an unreleased feature). Review the changelog guidelines.
  • Note: beta or "experiment" features that have active users should announce fixes in the changelog.
  • If this is not a feature or fix, use an appropriate type from the title guidelines. For example, telemetry-only changes should use the telemetry type.

[amazon-inspector-ohio]

✅ I finished the code review, and didn't find any security or code quality issues.