Add note about which namespace is used for game serves deployed from fleets

[mikeseese]

What type of PR is this?

Uncomment only one /kind <> line, press enter to put that in a new line, and remove leading whitespace from that line:

/kind breaking
/kind bug
/kind cleanup

/kind documentation

/kind feature
/kind hotfix
/kind release

What this PR does / Why we need it:

This PR provides additional context about where GameServer resources are deployed from when instantiated by Fleet's. Specifically, this addition attempts to remove confusion for those thinking that the helm chart value gameservers.namespaces changes where game servers are deployed by explicitly stating they deploy where the fleet is deployed. In the event that someone deploys a Fleet on a namespace that isn't included in the helm chart value gameservers.namespaces, they will end up receiving the error:

error looking up service account agones-system/agones-sdk: serviceaccount "agones-sdk" not found

similar to #146 and #1370 (references included for others in the same situation as me finding those posts via Google).

This PR attempts to prevent users from getting into this scenario in the first place.

Which issue(s) this PR fixes:

N/A

Special notes for your reviewer:
This PR was the result of this Slack thread

[aimuz]

/lgtm

[agones-bot]

Build Succeeded 👏

Build Id: ff625070-9fdd-472c-924b-0e90cb4ba4ed

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:1.34.0-dev-20fe945-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.34.0-dev-20fe945-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.34.0-dev-20fe945-linux-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.34.0-dev-20fe945-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.34.0-dev-20fe945-amd64
• Linux C++ SDK (build): agonessdk-1.34.0-dev-20fe945-amd64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.34.0-dev-20fe945-amd64.zip

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

• https://20fe945-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/3288/head:pr_3288 && git checkout pr_3288
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.34.0-dev-20fe945-amd64

[markmandel]

Sorry for the delay, was just dealing with some gnarly bugs.

Really good addition! Thanks for the contribution!

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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

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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 Failed 😱

Build Id: 75c039fa-b88c-4db5-8a8e-0bb13949737d

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• Cloud Build log download

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[agones-bot]

Build Succeeded 👏

Build Id: f311a70c-87c0-4594-91bf-71bc9c0c74fb

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:1.34.0-dev-77046b4-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.34.0-dev-77046b4-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.34.0-dev-77046b4-linux-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.34.0-dev-77046b4-amd64
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.34.0-dev-77046b4-amd64
• Linux C++ SDK (build): agonessdk-1.34.0-dev-77046b4-amd64-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.34.0-dev-77046b4-amd64.zip

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

• https://77046b4-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/3288/head:pr_3288 && git checkout pr_3288
• helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.34.0-dev-77046b4-amd64