Investigate how to optimize UI initialization

[Gudahtt]

What is this about?

We should investigate how slow each step of UI initialization is, and make plans to improve overall initialization time.

This would include everything from the start of the execution of ui.js to the initial render of the current page.

Scenario

No response

Design

No response

Technical Details

No response

Threat Modeling Framework

No response

Acceptance Criteria

• We have investigated UI initialization performance and written up a report about it
  • This could be shared just as a GitHub comment
• Separate issues have been created for each identified opportunity for optimizing performance

Stakeholder review needed before the work gets merged

• [X] Engineering (needed in most cases)
• [ ] Design
• [ ] Product
• [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
• [ ] Security
• [ ] Legal
• [ ] Marketing
• [ ] Management (please specify)
• [ ] Other (please specify)

References

No response

[davidmurdoch]

from the start of the execution of ui.js to the initial render of the current page

I think we should collect metrics from the start of page navigation, not just the start of execution of ui.js.

[metamaskbot]

Missing release label release-12.2.0 on issue. Adding release label release-12.2.0 on issue, as issue is linked to PR #26636 which has this release label.