All gRPC tests should use new testing package

[colin-axner]

Summary

In #140 I noticed some gRPC tests were not using the new testing package. The test case that req = nil can only be tested with the new testing package. We should update all tests and remove any old testing code for this setup. It is much easier to maintain the new testing code

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[crodriguezvega]

I think the idea would be to get rid of queryClient field in the test suites for:

• transfer
• 29-fee
• 02-client

And call instead the gRPC endpoint using the method in the keeper. For example: for transfer instead of doing suite.queryClient.DenomTrace, call suite.chainA.GetSimApp().TransferKeeper.DenomTrace.

[expertdicer]

Can you please review my changes? Thank you