contrib/google.golang.org/grpc: add WithErrorCheck option

[BIwashi]

What does this PR do?

This PR adds a new option called WithErrorCheck which allows users to set a custom function to determine whether an error should not be considered as an error for tracing purposes before sending it to DataDog.

Motivation

There are cases where an application produces errors, but they should not be sent to DataDog as errors. While the WithErrorCheck option allows for not treating specific gRPC status codes as errors, there are use cases where a more granular decision is needed based on the specific error, rather than just the status code.
For example, a user might want to consider a NotFound error as non-error for a specific RPC.

example

opts = []rpc.Option{
	...
	rpc.WithUnaryInterceptors(
		ddgrpc.UnaryServerInterceptor(
			ddgrpc.WithErrorCheck(func(method string, err error) bool {
				if err == nil {
					return true
				}
				errCode := status.Code(err)
				if errCode == codes.NotFound && method == "/example.ExampleService/GetInfo" {
					return true
				}
				return false
			}),
		),
	),
	...
}
...
rpcServer = rpc.NewServer(rpcHandler, opts...)

Describe how to test/QA your changes

Unit tests are included.

Reviewer's Checklist

• Changed code has unit tests for its functionality.
• If this interacts with the agent in a new way, a system test has been added.

[dianashevchenko]

Hi @BIwashi, thank you for the contribution! I think it wouldn't hurt to add some unit tests covering the NonErrorFunc option.

[BIwashi]

@dianashevchenko
I added unit tests for the NonErrorFunc option!
50c90b2
How does this implementation look to you? I would appreciate your feedback.

[dianashevchenko]

Suggested change

	var (
	rig *rig
	err error
	)
	if tt.nonErrorFunc == nil {
	rig, err = newRig(true)
	} else {
	rig, err = newRig(true, NonErrorFunc(tt.nonErrorFunc))
	}
	var opts []Option
	if tt.nonErrorFunc != nil {
	opts = append(opts, NonErrorFunc(tt.nonErrorFunc))
	}
	rig, err := newRig(true, opts...)

[dianashevchenko]

Please move the start of the mocktracer this into the test case run

[BIwashi]

Is this the correct revision of your point?
4fca224

[ajgajg1134]

See comment on proposal here: #2043 (comment)

[BIwashi]

I apologize for the delay in making the corrections. It would be much appreciated if you could take the time to review the revisions again. Thanks.
@dianashevchenko cc @ajgajg1134