Fix bech32 encoding

[greg-szabo]

PubKey::to_bech32() is not compatible with the Cosmos-SDK/Tendermint-Go implementation.

Go still uses Amino encoding before converting the public key into a bech32-encoded string.

This causes issues for KMS: iqlusioninc/tmkms#228

See the SDK code that implements the difference: https://github.com/cosmos/cosmos-sdk/blob/590358652cc1cbc13872ea1659187e073ea38e75/types/address.go#L634-L639

Cleanup effort here: cosmos/cosmos-sdk#7357

[greg-szabo]

The difference described on the above link in the SDK needs to be implemented here:

tendermint-rs/tendermint/src/public_key.rs

Lines 160 to 162 in 0fc7f40

	pub fn to_bech32(self, hrp: &str) -> String {
	bech32::encode(hrp, self.as_bytes())
	}