Allow mapping of Timestamp to Instant

### Problem

In 100s of places thought the Hedera node we convert Timestamps to and from Instants. It would be nice to avoid all that effort, engineer time and at runtime.

### Solution

Add a special comment config in protobuf files to map a protobuf message like `Timestamp` that has two fields second and nanos to a `java.time.Instant`. If that feature is enabled then replace all references to the protobuf message that has the comment to use `Instant` instead. So if another message has a field of type `Timestamp` it will now be of type `Instant`.

### Alternatives

_No response_