fix: de-bounce buttons on Governance actions

[maxwellmattryan]

Summary

Please summarize your changes, describing what they are and why they were made.

The register proposal popup needed to be slightly more robust.

Changelog

- Add de-bouncing / spinner to action button in register proposal popup
- Improve error handling around registering a proposal
- Cleanup some import statements, mainly alphabetizing them

Relevant Issues

Please list any related issues using development keywords.

Closes #5480

Testing

Platforms

Please select any platforms where your changes have been tested.

• Desktop
  • MacOS
  • Linux
  • Windows
• Mobile
  • iOS
  • Android

Instructions

Please describe the specific instructions, configurations, and/or test cases necessary to test and verify that your changes work as intended.

Test registering a proposal, trying invalid event IDs, valid (but non-existent) event IDs, invalid node URLs, etc.

Checklist

Please tick all of the following boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or modified tests that prove my changes work as intended
• I have verified that new and existing unit tests pass locally with my changes
• I have verified that my latest changes pass CI workflows for testing and linting
• I have made corresponding changes to the documentation