Reduce Bundle Size by making select2 loading optional

What does this MR do?

Reduces the bundle size of JS by loading Select2 only on demand. This should save 145 KB (of total of 2.35MB) on parsed size of main.js.

What are the relevant issue numbers?

Closes #56988 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer