Validate keys in tablet management iterator seek

[keith-turner]

The tablet management iterator should validate the ranges it receives in seek to ensure they work well for the whole row iterator and also ensure the range does not start or stop in the middle of a tablet.

One possible way to do this validation is to check that if keys exist in the range that columns are not set. If the range does not meet expectations then an exception should be thrown. The offending range should be included in a log message and/or the exception.

This would be a follow on improvement to #4457.