Upgrade to tm version 23.0. (#1927)

* Start upgrade. Currently go test ./... hangs.

* (squash this) Fix staking tests

* wip

* note what changes need to be made to make this work on tm v0.23.0

* Fix addr -> pubkey map

* cleanup code

* Fix slashing test failures except for begin blocker

* fix all slashing tests

* fix lcd tests

* Address PR comments

* add link to changelog.

* (wip) start making addrToPubkey map persisted. Since amino can't handle maps,
we have to change from what this commit is doing.

* Use the correct method of storing a map

* (squash this) address PR comments

* Did you run 'make'?

* remove gaiadebug binary

docs/sdk/core/examples/app2.go

@@ -183,7 +183,7 @@ type app2Tx struct {
 	sdk.Msg
 
 	PubKey    crypto.PubKey
-	Signature crypto.Signature
+	Signature []byte
 }
 
 // This tx only has one Msg.
@@ -191,7 +191,7 @@ func (tx app2Tx) GetMsgs() []sdk.Msg {
 	return []sdk.Msg{tx.Msg}
 }
 
-func (tx app2Tx) GetSignature() crypto.Signature {
+func (tx app2Tx) GetSignature() []byte {
 	return tx.Signature
 }