Improve operator registry and plugin loading

[kaixi-wang]

• reduce the number of times plugins are reloaded by listing operators from a global registry
• add method for forcing refresh of the registry
• for delegated operations, only run enabled operations
• disable plugins if missing requirements to run

This should prevent errors like:

Delegated operation service running

To exit, press ctrl + c
Failed to register operators for plugin @jacobmarks/twilio_automation

Running operation 6529bbd8de97d1438e00bd89 (@jacobmarks/fuzzy_search/create_text_index)
Failed to register operators for plugin @jacobmarks/twilio_automation
 100% |███████████████████████████████████████████████████████████████████████████████████████████████| 193/193 [2.6m elapsed, 0s remaining, 0.8 samples/s]
Failed to register operators for plugin @jacobmarks/twilio_automation
Operation 6529bbd8de97d1438e00bd89 complete
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation
Failed to register operators for plugin @jacobmarks/twilio_automation

What changes are proposed in this pull request?

(Please fill in changes proposed in this fix)

How is this patch tested? If it is not, please explain why.

(Details)

Release Notes

Is this a user-facing change that should be mentioned in the release notes?

• [ ] No. You can skip the rest of this section.
• [ ] Yes. Give a description of this change to be included in the release notes for FiftyOne users.

(Details in 1-2 sentences. You can just refer to another PR with a description if this PR is part of a larger change.)

What areas of FiftyOne does this PR affect?

• [ ] App: FiftyOne application changes
• [ ] Build: Build and test infrastructure changes
• [ ] Core: Core fiftyone Python library changes
• [ ] Documentation: FiftyOne documentation changes
• [ ] Other