Param Change Proposal

[alexanderbez]

This PR addresses the implementation of parameter change proposals. It's major features and changes include:

• Minor updates to the x/param module
  • Cleanup and moving types to types/ package
  • New ParameterChangeProposal and ParamChange types
• Updates to the x/gov module
  • Cleanup and moving types to types/ package
  • Disable SoftwareUpgrade proposals
  • Implement Content and Handler interfaces
  • Implement and use internal Content router in the keeper
  • Update EndBlocker to execute Content handler
• Update docs
• Update client functionality

This is state machine breaking. The proposal's Content JSON field has been renamed and SoftwareUpgrade are temporarily disabled.

A follow up PR should be made to add param change proposals to simulation.

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replaces/supersedes: #3880
closes: #3565

credit: @mossid

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• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry: sdkch add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[rigelrozanski]

Well done! - Good design, and nice refactors.

general comments on the docs, and code structure - nothing too big.

[codecov]

Codecov Report

Merging #4206 into master will increase coverage by 0.27%.
The diff coverage is 48.33%.

@@            Coverage Diff             @@
##           master    #4206      +/-   ##
==========================================
+ Coverage   60.17%   60.45%   +0.27%     
==========================================
  Files         212      218       +6     
  Lines       15187    15355     +168     
==========================================
+ Hits         9139     9283     +144     
- Misses       5419     5432      +13     
- Partials      629      640      +11

[alexanderbez]

@rigelrozanski @cwgoes @mossid I've addressed all your comments :)

[rigelrozanski]

🥇