cloud,grpcutil: avoid pretty-printing nil gRPC status

[stevendanna]

In some cases, errors from the GCP library would be printed as

grpc:  [code 0/OK]

This was the result of a few interacting features and changes:

• The GCP library added an Unwrap() method to the error type they returned.

• Our errors library has code to manually unwrap errors.

• The underlying GCP error attempts to abstract over gRPC and HTTP errors. It implements a GRPCStatus() method that returns nil if the underlying issue was an HTTP issue.

• Our custom error printer in grpcutil would specially print anything that implements GRPCStatus(), regardless of the return value.

Here, I've updated the custom printer to ignore cases where GRPCStatus() returns nil.

Epic: CRDB-27642

Release note (bug fix): Fix a bug in which some GCP-related errors would be returned with an uninformative error.

[cockroach-teamcity]

This change is 

[knz]

with nit.

Reviewed 6 of 6 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @dt and @stevendanna)

---

pkg/util/grpcutil/grpc_err_redaction.go line 26 at r1 (raw file):

	// return true, but the retuned error will have no message and
	// a code of OK.
	if se := (interface{ GRPCStatus() *grpcStatus.Status })(nil); errors.As(err, &se) {

Since the errors library is going to call grpcSpecialCasePrintFn on every level of the error chain, don't use errors.As here, which also recurses.
You can use the same simple cast as is performed inside status.FromError already.

[stevendanna]

bors r=knz

[craig]

Build failed:

• Bazel Essential CI (Cockroach)

[stevendanna]

bors retry

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[shermanCRL]

Thank you!