Make all keepers pointers, use multiple initialization methods

[ValarDragon]

Description

This is an alternate design to #696 , I actually like this better. It doesn't involve sweeping breaking changes across the app tests. I think we get the benefits of split up methods, and pointers unless necessary to not use them, without sacrificing usability elsewhere. I think we can get the abstraction we want in a keepers module still, by making a method to go from app -> AppKeepers struct, but not force its use throughout. (This is also really low priority imo)

We are refactoring initializing keepers into five steps, using pointer refs to keepers the whole way through:

• Initializing keepers with special SDK tie-ins", e.g. UpgradeKeeper, ParamsKeeper, CrisisKeeper, CapabilityKeeper.
• Setup upgrade keeper store loaders for new modules
• Initialize all other keepers
• Setup all the hooks
• Setup upgrade migrations

Then we have all other prior logic for setting module managers. The module managers should likely have code deduplicated in a future PR.

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[codecov-commenter]

Codecov Report

Merging #697 (40ba52e) into main (92ed4d9) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main     #697   +/-   ##
=======================================
  Coverage   18.69%   18.69%           
=======================================
  Files         171      171           
  Lines       23814    23814           
=======================================
  Hits         4452     4452           
  Misses      18600    18600           
  Partials      762      762           

Impacted Files	Coverage Δ
app/upgrades/v4/prop12.go	60.00% <0.00%> (ø)
app/upgrades/v4/upgrades.go	100.00% <ø> (ø)

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[mattverse]

LGTM!
I like how this change affects app.go in the way that it became so much easier to understand and modulized as well!

[UnityChaos]

Overall LGTM. Just pointed out some areas where it didn't make sense to me why some keepers were pointers and some were not. (I assume there are reasons)