refactor: moving value codecs to a single place

[tac0turtle]

Description

This proposes moving the math value codec into types to reduce the dependency graph in math. Don't want to have collections as a dep for people who aren't using it in a small library

would love to hear feedback from @testinginprod, if this is okay

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[testinginprod]

I think the change makes sense to me, in my head initially I though that a collections codec should live where we declare the type so that developers can find it easily.

Otherwise another solution might be to declare every codec in the SDK in a single package. We just need to find a way to make the codecs findable by developers.

[tac0turtle]

I think the change makes sense to me, in my head initially I though that a collections codec should live where we declare the type so that developers can find it easily.

Otherwise another solution might be to declare every codec in the SDK in a single package. We just need to find a way to make the codecs findable by developers.

I think for more used items yes, but generally would love to see a world where we don't use castTypes and other proto features in this way and only use native proto types.

[julienrbrt]

Included in https://github.com/cosmos/cosmos-sdk/releases/tag/math%2Fv1.0.0-beta.6