Instancify Engine Object

[HexaField]

Summary

all usage of Engine. is now Engine.instance.

References

#5834

Checklist

• CI/CD checks pass npm run check
  • Linter passing via npm run lint
  • Typescript passing via npm run check-errors
  • Unit & Integration tests passing via npm run test
  • Docker build process passing via npm run build-client
• If this PR is still a WIP, convert to a draft
• When this PR is ready, mark it as "Ready for review"
• Changes have been manually QA'd
• Changes reviewed by at least 2 approved reviewers

QA Steps

List any additional steps required to QA the changes of this PR, as well as any supplemental images or videos.

Reviewers

Reviewers for this PR

[NPatel10]

Only concern I have is whether it is going to have any impact on performance. Since property access chain became longer.