fix: #425 - protobuf upgrade

[MLCarey321]

Issue #, if available: #425

Description of changes:
Upgraded protobuf from github.com/golang/protobuf v1.5.3 to google.golang.org/protobuf v1.33.0. Required updates to some other dependencies, mainly github.com/grpc-ecosystem/go-grpc-middleware v1.3.0 to github.com/grpc-ecosystem/go-grpc-middleware/v2 v2.1.0. Because the naming conventions are more explicit in v2, I also had to update some of the types used in grpc_test.go.

I'll note that the tests fail, but with the same failure as they did when I ran the tests before making any changes, namely:

--- FAIL: TestBadRoundTripDial (0.08s)
    client_test.go:392: 
        	Error Trace:	/aws-xray-sdk-go/xray/client_test.go:392
        	Error:      	An error is expected but got nil.
        	Test:       	TestBadRoundTripDial
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x30 pc=0x105782690]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[MLCarey321]

Not sure who can/should review, but I see that @wangzlei is the only user that both commented on #425 that I am able to tag. :)

[MLCarey321]

I opened issue #471 for the failing test -- I'm getting this same error when I run make test from master with no changes.

[MLCarey321]

@wangzlei I don't have access to a Window's machine for testing and I'm not sure why the test is failing -- it's in capture_test.go:74, which shouldn't have been affected by my changes...

[MLCarey321]

@wangzlei What are the next steps here?