CIP: Make security related governance parameters immutable

This post is to discuss docs: CIP for make security related governance parameters immutable by caomingpei · Pull Request #74 · celestiaorg/CIPs · GitHub

// Motivation: Addressing Inconsistency in Governance Parameters celestiaorg/CIPs/pull#68

Notes from CDC 6:

1. consensus.evidence.MaxAgeNumBlocks is set at 120960 – this is currently based on an expected 15 second block time, but since blocks on Celestia are around 12 seconds, this time is more like 18 days. (Feedback from @ebuchman)
2. It may be good to add more parameters to this CIP or in the future, make a similar CIP. After discussion in call, it seems that it is best to make a new CIP after CIP-0016 is implemented.