feat!: remove legacy REST (#9594)

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## Description

ref: #7517

  * [x] Remove the x/{module}/client/rest folder
  * [x] Remove all glue code between simapp/modules and the REST server

<!-- Add a description of the changes that this PR introduces and the files that
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---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [x] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [x] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification - see #9615
- [x] reviewed "Files changed" and left comments if necessary
- [x] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [x] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [x] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed
- [ ] reviewed state machine logic
- [x] reviewed API design and naming
- [ ] reviewed documentation is accurate - see #9615
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

(cherry picked from commit cd22168)

# Conflicts:
#	CHANGELOG.md
#	client/tx/tx.go
#	codec/amino_codec_test.go
#	x/auth/client/cli/query.go
#	x/auth/client/rest/broadcast.go
#	x/auth/client/rest/decode.go
#	x/auth/client/rest/encode.go
#	x/auth/client/rest/rest_test.go
#	x/authz/client/testutil/grpc.go
#	x/bank/client/rest/query_test.go
#	x/bank/client/rest/tx_test.go
#	x/gov/client/testutil/grpc.go
#	x/mint/client/testutil/grpc.go
#	x/params/client/testutil/grpc.go
#	x/slashing/client/testutil/grpc.go
#	x/staking/client/testutil/grpc.go

CHANGELOG.md

@@ -41,7 +41,31 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 * [\#9860](https://github.com/cosmos/cosmos-sdk/pull/9860) Emit transaction fee in ante handler fee decorator. The event type is `tx` and the attribute is `fee`.
 
+<<<<<<< HEAD
 ### Improvements
+=======
+### API Breaking Changes
+
+* [\#9628](https://github.com/cosmos/cosmos-sdk/pull/9628) Rename `x/{mod}/legacy` to `x/{mod}/migrations`.
+* [\#9571](https://github.com/cosmos/cosmos-sdk/pull/9571) Implemented error handling for staking hooks, which now return an error on failure.
+* [\#9427](https://github.com/cosmos/cosmos-sdk/pull/9427) Move simapp `FundAccount` and `FundModuleAccount` to `x/bank/testutil`
+* (client/tx) [\#9421](https://github.com/cosmos/cosmos-sdk/pull/9421/) `BuildUnsignedTx`, `BuildSimTx`, `PrintUnsignedStdTx` functions are moved to
+  the Tx Factory as methods.
+* (x/slashing) [\#9458](https://github.com/cosmos/cosmos-sdk/pull/9458) Coins burned from slashing is now returned from Slash function and included in Slash event.
+* [\#9246](https://github.com/cosmos/cosmos-sdk/pull/9246) The `New` method for the network package now returns an error.
+* (codec) [\#9521](https://github.com/cosmos/cosmos-sdk/pull/9521) Removed deprecated `clientCtx.JSONCodec` from `client.Context`.
+* (codec) [\#9521](https://github.com/cosmos/cosmos-sdk/pull/9521) Rename `EncodingConfig.Marshaler` to `Codec`.
+* [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) `RESTHandlerFn` argument is removed from the `gov/NewProposalHandler`.
+* [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) `types/rest` package moved to `testutil/rest`.
+
+
+### Client Breaking Changes
+
+* [\#9594](https://github.com/cosmos/cosmos-sdk/pull/9594) Remove legacy REST API. Please see the [REST Endpoints Migration guide](https://docs.cosmos.network/master/migrations/rest.html) to migrate to the new REST endpoints.
+
+
+### CLI Breaking Changes
+>>>>>>> cd221680c (feat!: remove legacy REST  (#9594))
 
 * (deps) [\#9956](https://github.com/cosmos/cosmos-sdk/pull/9956) Bump Tendermint to [v0.34.12](https://github.com/tendermint/tendermint/releases/tag/v0.34.12).
 

client/docs/config.json

@@ -1,17 +1,11 @@
 {
   "swagger": "2.0",
   "info": {
-    "title": "Cosmos SDK - Legacy REST and gRPC Gateway docs",
-    "description": "A REST interface for state queries, legacy transactions",
+    "title": "Cosmos SDK - gRPC Gateway docs",
+    "description": "A REST interface for state queries",
     "version": "1.0.0"
   },
   "apis": [
-    {
-      "url": "./client/docs/swagger_legacy.yaml",
-      "dereference": {
-        "circular": "ignore"
-      }
-    },
     {
       "url": "./tmp-swagger-gen/cosmos/auth/v1beta1/query.swagger.json",
       "operationIds": {