kv/tscache: create new IntervalSkl encode/decode benchmarks

```
name                                                             time/op
IntervalSklDecodeValue/logical=false,synthetic=false,txnID=false-16  11.7ns ± 2%
IntervalSklDecodeValue/logical=false,synthetic=false,txnID=true-16   11.7ns ± 1%
IntervalSklDecodeValue/logical=false,synthetic=true,txnID=false-16   11.8ns ± 1%
IntervalSklDecodeValue/logical=false,synthetic=true,txnID=true-16    11.7ns ± 0%
IntervalSklDecodeValue/logical=true,synthetic=false,txnID=false-16   11.7ns ± 2%
IntervalSklDecodeValue/logical=true,synthetic=false,txnID=true-16    11.7ns ± 1%
IntervalSklDecodeValue/logical=true,synthetic=true,txnID=false-16    11.7ns ± 1%
IntervalSklDecodeValue/logical=true,synthetic=true,txnID=true-16     11.7ns ± 2%
IntervalSklEncodeValue/logical=false,synthetic=false,txnID=false-16  6.25ns ± 1%
IntervalSklEncodeValue/logical=false,synthetic=false,txnID=true-16   6.25ns ± 1%
IntervalSklEncodeValue/logical=false,synthetic=true,txnID=false-16   6.23ns ± 2%
IntervalSklEncodeValue/logical=false,synthetic=true,txnID=true-16    6.23ns ± 2%
IntervalSklEncodeValue/logical=true,synthetic=false,txnID=false-16   6.26ns ± 3%
IntervalSklEncodeValue/logical=true,synthetic=false,txnID=true-16    6.24ns ± 1%
IntervalSklEncodeValue/logical=true,synthetic=true,txnID=false-16    6.29ns ± 3%
IntervalSklEncodeValue/logical=true,synthetic=true,txnID=true-16     6.23ns ± 2%

name                                                             alloc/op
IntervalSklDecodeValue/logical=false,synthetic=false,txnID=false-16   0.00B
IntervalSklDecodeValue/logical=false,synthetic=false,txnID=true-16    0.00B
IntervalSklDecodeValue/logical=false,synthetic=true,txnID=false-16    0.00B
IntervalSklDecodeValue/logical=false,synthetic=true,txnID=true-16     0.00B
IntervalSklDecodeValue/logical=true,synthetic=false,txnID=false-16    0.00B
IntervalSklDecodeValue/logical=true,synthetic=false,txnID=true-16     0.00B
IntervalSklDecodeValue/logical=true,synthetic=true,txnID=false-16     0.00B
IntervalSklDecodeValue/logical=true,synthetic=true,txnID=true-16      0.00B
IntervalSklEncodeValue/logical=false,synthetic=false,txnID=false-16   0.00B
IntervalSklEncodeValue/logical=false,synthetic=false,txnID=true-16    0.00B
IntervalSklEncodeValue/logical=false,synthetic=true,txnID=false-16    0.00B
IntervalSklEncodeValue/logical=false,synthetic=true,txnID=true-16     0.00B
IntervalSklEncodeValue/logical=true,synthetic=false,txnID=false-16    0.00B
IntervalSklEncodeValue/logical=true,synthetic=false,txnID=true-16     0.00B
IntervalSklEncodeValue/logical=true,synthetic=true,txnID=false-16     0.00B
IntervalSklEncodeValue/logical=true,synthetic=true,txnID=true-16      0.00B

name                                                             allocs/op
IntervalSklDecodeValue/logical=false,synthetic=false,txnID=false-16    0.00
IntervalSklDecodeValue/logical=false,synthetic=false,txnID=true-16     0.00
IntervalSklDecodeValue/logical=false,synthetic=true,txnID=false-16     0.00
IntervalSklDecodeValue/logical=false,synthetic=true,txnID=true-16      0.00
IntervalSklDecodeValue/logical=true,synthetic=false,txnID=false-16     0.00
IntervalSklDecodeValue/logical=true,synthetic=false,txnID=true-16      0.00
IntervalSklDecodeValue/logical=true,synthetic=true,txnID=false-16      0.00
IntervalSklDecodeValue/logical=true,synthetic=true,txnID=true-16       0.00
IntervalSklEncodeValue/logical=false,synthetic=false,txnID=false-16    0.00
IntervalSklEncodeValue/logical=false,synthetic=false,txnID=true-16     0.00
IntervalSklEncodeValue/logical=false,synthetic=true,txnID=false-16     0.00
IntervalSklEncodeValue/logical=false,synthetic=true,txnID=true-16      0.00
IntervalSklEncodeValue/logical=true,synthetic=false,txnID=false-16     0.00
IntervalSklEncodeValue/logical=true,synthetic=false,txnID=true-16      0.00
IntervalSklEncodeValue/logical=true,synthetic=true,txnID=false-16      0.00
IntervalSklEncodeValue/logical=true,synthetic=true,txnID=true-16       0.00
```

pkg/kv/kvserver/tscache/interval_skl_test.go

@@ -1381,3 +1381,44 @@ func randRange(rng *rand.Rand, slots int) (from, middle, to []byte) {
 func randRangeOpt(rng *rand.Rand) rangeOptions {
 	return rangeOptions(rng.Intn(int(excludeFrom|excludeTo) + 1))
 }
+
+func BenchmarkIntervalSklDecodeValue(b *testing.B) {
+	runBenchWithVals(b, func(b *testing.B, val cacheValue) {
+		var arr [encodedValSize]byte
+		enc := encodeValue(arr[:0], val)
+		for i := 0; i < b.N; i++ {
+			_, _ = decodeValue(enc)
+		}
+	})
+}
+
+func BenchmarkIntervalSklEncodeValue(b *testing.B) {
+	runBenchWithVals(b, func(b *testing.B, val cacheValue) {
+		var arr [encodedValSize]byte
+		for i := 0; i < b.N; i++ {
+			_ = encodeValue(arr[:0], val)
+		}
+	})
+}
+
+func runBenchWithVals(b *testing.B, fn func(*testing.B, cacheValue)) {
+	for _, withLogical := range []bool{false, true} {
+		for _, withSynthetic := range []bool{false, true} {
+			for _, withTxnID := range []bool{false, true} {
+				var val cacheValue
+				val.ts.WallTime = 15
+				if withLogical {
+					val.ts.Logical = 10
+				}
+				if withSynthetic {
+					val.ts.Synthetic = true
+				}
+				if withTxnID {
+					val.txnID = uuid.MakeV4()
+				}
+				name := fmt.Sprintf("logical=%t,synthetic=%t,txnID=%t", withLogical, withSynthetic, withTxnID)
+				b.Run(name, func(b *testing.B) { fn(b, val) })
+			}
+		}
+	}
+}