ADR-019/020 cleanups: HybridCodec, Pubkey (#8683)

* wip adr019

* Remove hybrid codec

* Change date

* Update docs/architecture/adr-019-protobuf-state-encoding.md

Co-authored-by: Robert Zaremba <robert@zaremba.ch>

* Update pubkey interface

Co-authored-by: Robert Zaremba <robert@zaremba.ch>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

docs/architecture/adr-019-protobuf-state-encoding.md

@@ -7,6 +7,7 @@
 - 2020 Apr 27: Convert usages of `oneof` for interfaces to `Any`
 - 2020 May 15: Describe `cosmos_proto` extensions and amino compatibility
 - 2020 Dec 4: Move and rename `MarshalAny` and `UnmarshalAny` into the `codec.Marshaler` interface.
+- 2021 Feb 24: Remove mentions of `HybridCodec`, which has been abandoned in [#6843](https://github.com/cosmos/cosmos-sdk/pull/6843).
 
 ## Status
 
@@ -59,24 +60,26 @@ We will adopt [Protocol Buffers](https://developers.google.com/protocol-buffers)
 persisted structured data in the Cosmos SDK while providing a clean mechanism and developer UX for
 applications wishing to continue to use Amino. We will provide this mechanism by updating modules to
 accept a codec interface, `Marshaler`, instead of a concrete Amino codec. Furthermore, the Cosmos SDK
-will provide three concrete implementations of the `Marshaler` interface: `AminoCodec`, `ProtoCodec`,
-and `HybridCodec`.
+will provide two concrete implementations of the `Marshaler` interface: `AminoCodec` and `ProtoCodec`.
 
 - `AminoCodec`: Uses Amino for both binary and JSON encoding.
-- `ProtoCodec`: Uses Protobuf for or both binary and JSON encoding.
-- `HybridCodec`: Uses Amino for JSON encoding and Protobuf for binary encoding.
+- `ProtoCodec`: Uses Protobuf for both binary and JSON encoding.
 
-Until the client migration landscape is fully understood and designed, modules will use a `HybridCodec`
-as the concrete codec it accepts and/or extends. This means that all client JSON encoding, including
-genesis state, will still use Amino. The ultimate goal will be to replace Amino JSON encoding with
-Protbuf encoding and thus have modules accept and/or extend `ProtoCodec`.
+Modules will use whichever codec that is instantiated in the app. By default, the SDK's `simapp`
+instantiates a `ProtoCodec` as the concrete implementation of `Marshaler`, inside the `MakeTestEncodingConfig`
+function. This can be easily overwritten by app developers if they so desire.
+
+The ultimate goal will be to replace Amino JSON encoding with Protobuf encoding and thus have
+modules accept and/or extend `ProtoCodec`. Until then, Amino JSON is still provided for legacy use-cases.
+A handful of places in the SDK still have Amino JSON hardcoded, such as the Legacy API REST endpoints
+and the `x/params` store. They are planned to be converted to Protobuf in a gradual manner.
 
 ### Module Codecs
 
 Modules that do not require the ability to work with and serialize interfaces, the path to Protobuf
 migration is pretty straightforward. These modules are to simply migrate any existing types that
 are encoded and persisted via their concrete Amino codec to Protobuf and have their keeper accept a
-`Marshaler` that will be a `HybridCodec`. This migration is simple as things will just work as-is.
+`Marshaler` that will be a `ProtoCodec`. This migration is simple as things will just work as-is.
 
 Note, any business logic that needs to encode primitive types like `bool` or `int64` should use
 [gogoprotobuf](https://github.com/gogo/protobuf) Value types.
@@ -207,7 +210,7 @@ Note that `InterfaceRegistry` usage does not deviate from standard protobuf
 usage of `Any`, it just introduces a security and introspection layer for
 golang usage.
 
-`InterfaceRegistry` will be a member of `ProtoCodec` and `HybridCodec` as
+`InterfaceRegistry` will be a member of `ProtoCodec` 
 described above. In order for modules to register interface types, app modules
 can optionally implement the following interface:
 

docs/architecture/adr-020-protobuf-transaction-encoding.md

@@ -12,6 +12,7 @@
 - 2020 August 19: Move sequence field from `SignDoc` to `SignerInfo`, as discussed in [#6966](https://github.com/cosmos/cosmos-sdk/issues/6966).
 - 2020 September 25: Remove `PublicKey` type in favor of `secp256k1.PubKey`, `ed25519.PubKey` and `multisig.LegacyAminoPubKey`.
 - 2020 October 15: Add `GetAccount` and `GetAccountWithHeight` methods to the `AccountRetriever` interface.
+- 2021 Feb 24: The SDK does not use Tendermint's `PubKey` interface anymore, but its own `cryptotypes.PubKey`. Updates to reflect this.
 
 ## Status
 
@@ -286,7 +287,7 @@ and `FileDescriptor`s and returns a boolean result.
 
 ### Public Key Encoding
 
-Public keys in the Cosmos SDK implement Tendermint's `crypto.PubKey` interface.
+Public keys in the Cosmos SDK implement the `cryptotypes.PubKey` interface.
 We propose to use `Any` for protobuf encoding as we are doing with other interfaces (e.g. in `BaseAccount` `PubKey` or `SignerInfo` `PublicKey`).
 Following public keys are implemented: secp256k1, ed25519 and multisignature.