Implement native test for the gRPC / Hibernate ITs

[cescoffier]

Fix #22619

[alesj]

@cescoffier I would abstract those init/cleanup methods, so you don't have them duplicated all over the tests.

And there is a grpc-test-utils lib in test-framework module that already does all that - init and close.
So that we have this init/close handling at a single place; e.g. we might want to change how we close the GrpcClient(Channel)

[cescoffier]

@alesj It would requires introducing 3 new abstract classes with the same level of duplication.

The tests are already extending a class, so we are kind of limited. However, I can move some code into a helper class.

[cescoffier]

@alesj I pushed a new version reducing the code duplication.

[cescoffier]

@alesj can you have another look?