[KIP-286,290] Make CandInactive to Registered state

[hyeonLewis]

Proposed changes

• Rename CandInactive state to Registered to better reflect that entities in this state are not candidates — they
  are simply registered in the system
• Introduce a new Registration States category (Unknown, Registered) separate from Candidate States (CandReady,
  CandTesting), changing the state taxonomy from 2 categories to 3
• Update all transition tables, pseudo code, flowchart, and ordering rationale in KIP-286
• Update NodeState enum in KIP-290

Types of changes

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• Bugfix
• KIP Proposal
• KIP Improvement

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• Used the suggested template: https://github.com/kaiachain/KIPs/blob/main/kip-template.md
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• Any dependent changes have been merged and published in downstream modules

Related issues

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Further comments

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