ci: improve error checking (errcheck linter) (#11195)

## Description

Implements part of #7258

Check some of currently unchecked errors.

- [x] baseapp
- [x] client
- [x] codec
- [x] crypto
- [x] server
- [x] simapp
- [ ] snapshots
- [ ] store
- [x] testutil
- [ ] types
- [ ] modules

---

### 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/master/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/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/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)

crypto/keyring/keyring_test.go

@@ -1077,19 +1077,19 @@ func TestNonConsistentKeyring_SavePubKey(t *testing.T) {
 	priv := ed25519.GenPrivKey()
 	pub := priv.PubKey()
 
-	k, err := kr.SaveOfflineKey(key, pub)
-	require.Nil(t, err)
+	_, err = kr.SaveOfflineKey(key, pub)
+	require.NoError(t, err)
 
 	// broken keyring state test
 	unsafeKr, ok := kr.(keystore)
 	require.True(t, ok)
 	// we lost public key for some reason, but still have an address record
-	unsafeKr.db.Remove(infoKey(key))
+	require.NoError(t, unsafeKr.db.Remove(infoKey(key)))
 	list, err = kr.List()
 	require.NoError(t, err)
 	require.Equal(t, 0, len(list))
 
-	k, err = kr.SaveOfflineKey(key, pub)
+	k, err := kr.SaveOfflineKey(key, pub)
 	require.Nil(t, err)
 	pubKey, err := k.GetPubKey()
 	require.NoError(t, err)