fix: remove deprecated grpc.WithBlock

[salasberryfin]

What this PR does / why we need it:

gRPC's WithBlock is deprecated and using it will prevent us from updating google.golang.org/grpc.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #488

Special notes for your reviewer:

We can create a specific context and pass it to clientv3.Config so it manages timeouts and cancellations. This will prevent operations from hanging indefinitely.

Checklist:

• squashed commits into logical changes
• includes documentation
• adds unit tests
• adds or updates e2e tests

[furkatgofurov7]

@salasberryfin can we rebase this PR? Otherwise this LGTM

[yiannistri]

The change looks ok to me but I'm wondering if a linter suppression would be more appropriate at this point in time. Basically this comment seems to suggest that the WithBlock() behaviour can be substituted with additional code and I'm not sure whether the go.etcd.io/etcd/client/v3 v3.5.13 client that we use in CAPRKE2 right now will do the right thing or not. Perhaps we should consider upgrading the etcd client as well or perhaps I'm worrying about this too much 😕

Useful context: https://github.com/grpc/grpc-go/blob/master/Documentation/anti-patterns.md