Make it easier to track feature gaps with hbase api

Its very toilsome to keep https://cloud.google.com/bigtable/docs/hbase-differences upto date when upgrading hbase client versions and adding features.

We should introduce some tooling to generate a diff. I think the easiest way to do this is to separate implemented and unimplemented methods in different classes. For example we should introduce `AbstractBigtableAdmin1x` class that will contain only the implemented methods. Then we can create a concrete class BigtableAdmin that contains all of the methods that throw UnsupportedOperation exceptions. Then we can use reflection to generate a list of methods that we dont support