feat: discard disconnected game server streams

[antiphp]

What type of PR is this?

/kind feature

What this PR does / Why we need it:

This PR adds the ability for the SDK server to remove closed streams and only log once when a closed stream is found.
GRPC streams take a context, which is forwarded by the SDK, and when that context is cancelled, currently the SDK server starts logging repeatedly about the connection being closed.
With the changes from this pull request, what happens instead is that when a closed stream is found, an error is logged and it is then removed from the connectedStreams slice.
In order to know whether the stream is closed, we check the status of the stream.Context().

Unit tests are updated to cover all relevant cases due to the changes in this PR.

Which issue(s) this PR fixes:

Fixes #3327

Special notes for your reviewer:

The unit test is a copy&paste from the above test, just with an adjustment to test the removal of the stream.

This MR was also tested with a new build image for the sidecar, applied via agones-controller in Kubernetes.
The game server called the sidecar's WatchGameServer, and later cancelled the connection.

The fix reported the context cancellation once and removed the stream from the connected streams.

No more error reports.

[agones-bot]

Build Failed 😱

Build Id: 10bc5578-edd6-4631-b69e-030ab01fa90a

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[agones-bot]

Build Failed 😱

Build Id: 27be38fd-286a-4d48-ace8-c5e48cf34159

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[agones-bot]

Build Succeeded 👏

Build Id: a0fb9429-48a4-4d16-90ac-f79549f852c9

The following development artifacts have been built, and will exist for the next 30 days:

• image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.35.0-dev-1cdb6c4-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.35.0-dev-1cdb6c4-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.35.0-dev-1cdb6c4-linux-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.35.0-dev-1cdb6c4-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.35.0-dev-1cdb6c4-amd64
• Linux C++ SDK (build): agonessdk-1.35.0-dev-1cdb6c4-amd64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.35.0-dev-1cdb6c4-amd64.zip

A preview of the website (the last 30 builds are retained):

• https://1cdb6c4-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/3328/head:pr_3328 && git checkout pr_3328
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.35.0-dev-1cdb6c4-amd64

[markmandel]

Nice update! Thanks!

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: antiphp, markmandel

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Needs approval from an approver in each of these files:

• OWNERS [markmandel]

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[google-oss-prow]

New changes are detected. LGTM label has been removed.

[agones-bot]

Build Succeeded 👏

Build Id: 7a09118d-4123-4898-85ad-ba2be58335d6

The following development artifacts have been built, and will exist for the next 30 days:

• image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.35.0-dev-c20ddbf-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.35.0-dev-c20ddbf-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.35.0-dev-c20ddbf-linux-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.35.0-dev-c20ddbf-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.35.0-dev-c20ddbf-amd64
• Linux C++ SDK (build): agonessdk-1.35.0-dev-c20ddbf-amd64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.35.0-dev-c20ddbf-amd64.zip

A preview of the website (the last 30 builds are retained):

• https://c20ddbf-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/3328/head:pr_3328 && git checkout pr_3328
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.35.0-dev-c20ddbf-amd64