Use chainlink-commons for hash and merkle pkg in ocr3 (#1000)

## Motivation
With
[chainlink-common#527](smartcontractkit/chainlink-common#527)
hashlib (now hashutil) and merklemulti were moved to a common location.

## Solution
Update [ccip repo](https://github.com/smartcontractkit/ccip) to remove
`core/services/ocr3/plugins/ccip/internal/libs/hashlib/` and
`core/services/ocr3/plugins/ccip/internal/libs/merklemulti/`. Replace
them with the versions in chainlink-common.

## Future work
After the merge of [Merge core release
2.13.0](#988), this
refactor should be done also in
`./core/services/ocr2/plugins/ccip/pkg/hashlib/` and
`./core/services/ocr2/plugins/ccip/pkg/merklemulti/`.

.changeset/clever-hotels-call.md

@@ -0,0 +1,5 @@
+---
+"ccip": patch
+---
+
+use chainlink-common for hash and merklemulti in ocr3 #internal

core/services/ocr3/plugins/ccip/commit/plugin_functions.go

@@ -10,12 +10,13 @@ import (
 	"github.com/smartcontractkit/libocr/offchainreporting2plus/types"
 	"golang.org/x/sync/errgroup"
 
-	"github.com/smartcontractkit/ccipocr3/internal/libs/hashlib"
-	"github.com/smartcontractkit/ccipocr3/internal/libs/merklemulti"
 	"github.com/smartcontractkit/ccipocr3/internal/libs/slicelib"
 
 	"github.com/smartcontractkit/chainlink-common/pkg/logger"
 	cciptypes "github.com/smartcontractkit/chainlink-common/pkg/types/ccipocr3"
+
+	"github.com/smartcontractkit/chainlink-common/pkg/hashutil"
+	"github.com/smartcontractkit/chainlink-common/pkg/merklemulti"
 )
 
 // observeMaxSeqNums finds the maximum committed sequence numbers for each source chain.
@@ -364,7 +365,7 @@ func newMsgsConsensusForChain(
 	}
 
 	lggr.Debugw("constructing merkle tree", "chain", chainSel, "treeLeaves", len(treeLeaves))
-	tree, err := merklemulti.NewTree(hashlib.NewKeccakCtx(), treeLeaves)
+	tree, err := merklemulti.NewTree(hashutil.NewKeccak(), treeLeaves)
 	if err != nil {
 		return observedMsgsConsensus{}, fmt.Errorf("construct merkle tree from %d leaves: %w", len(treeLeaves), err)
 	}