Option comment parsing has issues

The `optionComment` defined in the Protobuf grammar can apply to individual top-level objects (such as a message definition), as well as to sub-items (e.g. individual fields inside the message.) However, it can also be a top-level option comment. For example, many test models define `pbj.java_package`. Example:

```
syntax = "proto3";

package proto;

option java_package = "com.hedera.pbj.test.proto.java";
option java_multiple_files = true;
// <<>> This comment is special code for setting PBJ Compiler java package

message NotCacheableAccountID {
```

The intention of the above code is to have the `pbj.java_package` be a "top-level option comment." However, per the parser grammar it actually applies to the `NotCacheableAccountID` message instead.

Need to see how to differentiate between the two...