fix: remove duplicate ante events (#13983)

## Description

After enabling the post-handler on our chain, we realised something odd with our transaction events. The ordering was `[ANTE, MSGS, ANTE, POST]`. After doing some digging, we realised that the context used inside the post-handler still contains the events from the ante-handler.

This should be backported to v0.46.x and v0.47.x 😄
Happy to make it compatible with #13940 when that gets merged!

cc @mbreithecker



---

### 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...

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

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

CHANGELOG.md

@@ -224,6 +224,7 @@ extension interfaces. `module.Manager.Modules` is now of type `map[string]interf
 * (x/gov) [#13918](https://github.com/cosmos/cosmos-sdk/pull/13918) Fix propagation of message errors when executing a proposal.
 * (baseapp)[#14049](https://github.com/cosmos/cosmos-sdk/pull/14049) Fix state sync when interval is zero.
 * (store) [#13516](https://github.com/cosmos/cosmos-sdk/pull/13516) Fix state listener that was observing writes at wrong time.
+* (baseapp) [#13983](https://github.com/cosmos/cosmos-sdk/pull/13983) Don't emit duplicate ante-handler events when a post-handler is defined.
 
 ### Deprecated
 

baseapp/baseapp.go

@@ -738,7 +738,12 @@ func (app *BaseApp) runTx(mode runTxMode, txBytes []byte) (gInfo sdk.GasInfo, re
 		//
 		// Note: If the postHandler fails, we also revert the runMsgs state.
 		if app.postHandler != nil {
-			newCtx, err := app.postHandler(runMsgCtx, tx, mode == runTxModeSimulate)
+			// The runMsgCtx context currently contains events emitted by the ante handler.
+			// We clear this to correctly order events without duplicates.
+			// Note that the state is still preserved.
+			postCtx := runMsgCtx.WithEventManager(sdk.NewEventManager())
+
+			newCtx, err := app.postHandler(postCtx, tx, mode == runTxModeSimulate)
 			if err != nil {
 				return gInfo, nil, nil, priority, err
 			}