Logging updates for handling consumer errors

[svairagade]

• FsKafka: Added filter to treat Fatal errors and warnings distinctly,
• FsKafka0: Added an observer OnConsumeError

[bartelink]

While these definitely add more context and hence are helpful, my main concern (as covered in comments) is to avoid varying the text unnecessary

Also, is the intent here to narrow down V0 vs V1 behavior differences? If so, should that be accomplished by an integration test ?