Refactor codec registry + remove consts package

[joshua-kim]

We have a strange structure in the packages where the codecs aren't even initialized in their own package. Need to move the initialization code to the same place the codecs are defined.

[aaronbuchwald]

Note: the intention here is to ensure that the action/auth registries can be imported from any package. We should still get rid of this because it's bizarre that the consts/ package would require importing a different package to make sure that it's correctly initialized.