refactor listInvites, add isGroup operator

[mixmix]

This PR:

• adds pull-defer as a tidier pattern for the "I need to async then I stream" problem
• removes some un-needed dependencies
  • multicb in favour of just using pull-streams
  • lodash.uniqby replaced by pull.unique() when set up right
  • lodash.get removed as we know we can rely on fields if passed pull.filter(isAddMember)
• adds a isGroup operator for faster querying of messages-by-group
  • :heavy_check_mark: tested!
  • :new: merged into master already in another PR
• breaks up some of the massive nested functions into chunks of function for easier reading

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Pull request alert summary

Issue	Status
Install scripts	✅ 0 issues
Native code	✅ 0 issues
Bin script shell injection	✅ 0 issues
Unresolved require	✅ 0 issues
Invalid package.json	✅ 0 issues
HTTP dependency	✅ 0 issues
Git dependency	✅ 0 issues
Deprecated license	✅ 0 issues
Missing license	✅ 0 issues
Potential typo squat	✅ 0 issues
Known Malware	✅ 0 issues
Telemetry	✅ 0 issues
Protestware/Troll package	✅ 0 issues

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📊 Modified Dependency Overview:

🚮 Removed packages: lodash.get@4.4.2, lodash.uniqby@4.7.0

[mixmix]

I'm working on splitting this PR out into some parts