R4R: Supply Module

[fedekunze]

Closes #3972
closes #3628
closes #4472

Full Spec: #4599

This PR creates a new x/supply module that passively keeps track of the total supply of the network. It introduces the concept of a ModuleAccount, which is a module/pool that holds or mint coins. The ModuleAccount address is created from the hash of a root string (aka ModuleAccount.Name).

Additionally, the supply Keeper has bank functionalities to transfer coins from and to an ModuleAccount using only its name.

With respect to breaking changes, this PR gets rid of all the pools of coins from store and replaces each of them with a ModuleAccount. The pools added/affected by this change are:

• auth: FeeCollectionKeeper replaced for a fee collector BaseAccount (to avoid import cycles)
• staking: the Pool was replaced for a NotBonded (held in staking as opposed to before) and Bonded ModuleAccount
• governance: deposit and burn addresses: for a gov ModuleAccount
• distribution: created a module ModuleAccount which controls the flow of coins into (from the fee collector acc) and out of the module store (to withdraw addresses).
• mint: created a module ModuleMinterAccount that is allowed to mint coins before redistributing them to the fee collector account.

TODOs:

• Fix simulation and invariance
• Fix tests
• NotBondedPool account should represent the coins only held in x/staking

---

• 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: clog add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

---

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)

[codecov]

Codecov Report

Merging #4255 into master will increase coverage by 0.2%.
The diff coverage is 62.75%.

@@            Coverage Diff            @@
##           master    #4255     +/-   ##
=========================================
+ Coverage   54.62%   54.83%   +0.2%     
=========================================
  Files         260      272     +12     
  Lines       16538    17020    +482     
=========================================
+ Hits         9034     9333    +299     
- Misses       6858     7001    +143     
- Partials      646      686     +40

[alexanderbez]

Good job @fedekunze! I left some initial feedback. I'm also still a bit confused as to the "AC" of this PR. I thought the supply keeper would be the module keeping track of all sorts of supplies (ie. the staking keeper will not store bonded/unbonded supply internally)?

[alexanderbez]

Looks like this PR isn't complete. Should we close @fedekunze ?

[sabau]

Tested, all good! What a massive work, thanks Fede!

[fedekunze]

I forgot to add the clog entry, will do it now

[alexanderbez]

ACK -- just a few more points of nitpicking.

[jackzampolin]

[alexanderbez]

ACK ⚡️ 🐸 🎉 💯