chore: Update release notes and Changelog for 0.42.6 (#9544)

* Update release notes

* Clean up changelog

Author: amaury1093

CHANGELOG.md

@@ -34,7 +34,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 # Changelog
 
-## Unreleased
+## [v0.42.6](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.42.6) - 2021-06-18
 
 ### Improvements
 
@@ -47,20 +47,13 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * [\#9385](https://github.com/cosmos/cosmos-sdk/pull/9385) Fix IBC `query ibc client header` cli command. Support historical queries for query header/node-state commands. 
 * [\#9401](https://github.com/cosmos/cosmos-sdk/pull/9401) Fixes incorrect export of IBC identifier sequences. Previously, the next identifier sequence for clients/connections/channels was not set during genesis export. This resulted in the next identifiers being generated on the new chain to reuse old identifiers (the sequences began again from 0).
 * [\#9408](https://github.com/cosmos/cosmos-sdk/pull/9408) Update simapp to use correct default broadcast mode.
-
 * [\#9513](https://github.com/cosmos/cosmos-sdk/pull/9513) Fixes testnet CLI command. Testnet now updates the supply in genesis. Previously, when using add-genesis-account and testnet together, inconsistent genesis files would be produced, as only add-genesis-account was updating the supply.
+* (x/gov) [\#8813](https://github.com/cosmos/cosmos-sdk/pull/8813) fix `GET /cosmos/gov/v1beta1/proposals/{proposal_id}/deposits` to include initial deposit
 
 ### Features
 
 * [\#9383](https://github.com/cosmos/cosmos-sdk/pull/9383) New CLI command `query ibc-transfer escrow-address <port> <channel id>` to get the escrow address for a channel; can be used to then query balance of escrowed tokens
 * (baseapp, types) [#\9390](https://github.com/cosmos/cosmos-sdk/pull/9390) Add current block header hash to `Context`
-
-### Bug Fixes
-
-* (x/gov) [\#8813](https://github.com/cosmos/cosmos-sdk/pull/8813) fix `GET /cosmos/gov/v1beta1/proposals/{proposal_id}/deposits` to include initial deposit
-
-### Improvements
-
 * (store) [\#9403](https://github.com/cosmos/cosmos-sdk/pull/9403) Add `RefundGas` function to `GasMeter` interface
 
 ## [v0.42.5](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.42.5) - 2021-05-18

RELEASE_NOTES.md

@@ -1,25 +1,22 @@
-# Cosmos SDK v0.42.5 "Stargate" Release Notes
+# Cosmos SDK v0.42.6 "Stargate" Release Notes
 
 This release includes various minor bugfixes and improvments, including:
 
-- Fix support for building the Cosmos SDK on ARM architectures,
-- Fix the `[appd] keys show/list` CLI subcommands for multisigs,
-- Internal code performance improvment.
+- x/bank's InitGenesis optimization, which should significantly decrease genesis initialization time,
+- bump Tendermint to v0.34.11 to fix state sync issues,
+- add `cosmos_sdk_version` to `node_info` to be able to query the SDK version used by a node,
+- IBC bugfixes and improvements (see below for more info),
+- new fields on `sdk.Context` (see below for more info).
 
-It also introduces one new feature: adding the `[appd] config` subcommand back to the SDK.
+See the [Cosmos SDK v0.42.6 milestone](https://github.com/cosmos/cosmos-sdk/milestone/45?closed=1) on our issue tracker for the exhaustive list of all changes.
 
-See the [Cosmos SDK v0.42.5 milestone](https://github.com/cosmos/cosmos-sdk/milestone/44?closed=1) on our issue tracker for the exhaustive list of all changes.
+### IBC Bugfixes and Improvements
 
-### The `config` Subcommand
+The `[appd] query ibc client header` is fixed and allows querying by height for the header and node-state command. This allows easier venerability of which IBC tokens belong to which chains. IBC's ExportGenesis now exports all fields, including previously missing `NextClientSequence`, `NextConnectionSequence` and `NextChannelSequence`. A new subcommand `[appd] query ibc-transfer escrow-address` has been added to get the escrow address for a channel; it can be used to then query balance of escrowed tokens.
 
-One new feature introduced in the Stargate series was the merging of the two CLI binaries `[appd]` and `[appcli]` into one single application binary. In this process, the `[appcli] config` subcommand, which was used to save client-side configuration into a TOML file, was removed.
+### New Fields on `sdk.Context`
 
-Due to [popular demand](https://github.com/cosmos/cosmos-sdk/issues/8529), we have introduced this feature back to the SDK, under the `[appd] config` subcommand. The functionality is as follows:
+Two fields have been added on `sdk.Context`:
 
-- `[appd] config`: Output all client-side configuration.
-- `[appd] config [config-name]`: Get the given configuration (e.g. `keyring-backend` or `node-id`).
-- `[appd] config [config-name] [config-value]`: Set and persist the given configuration with the new value.
-
-All configurations are persisted to the filesystem, under the path `$APP_HOME/config/client.toml`. For the list of all possible client-side configurations, please have a look at this `client.toml` file, as it is heavily commented.
-
-Environment variables binding to client-side configuration also works. For example, the command `KEYRING_BACKEND=os [appd] tx bank send ...` will bind ENV variable to the `keyring-backend` config. The order or precedence for config is: `flags > env vars > client.toml file`.
+- `ctx.HeaderHash` adds the current block header hash obtained during abci.RequestBeginBlock to the Context,
+- `ctx.GasMeter().RefundGas(<amount>, <description>)` adds support for refunding gas directly to the gas meter.