feat: use new errors pkg in pkg/gameserverallocations/*

[lacroixthomas]

What type of PR is this?
/kind cleanup

What this PR does / Why we need it:

Use the new error package (https://github.com/agones-dev/agones/blob/main/pkg/util/errors/errors.go) on the pkg/gameserverallocations/* files

Which issue(s) this PR fixes:

Work on #4510

Did you use AI tools in preparing this PR?:

Y

Special notes for your reviewer:

[agones-bot]

Build Failed 😭

Build Id: 4393800c-c8fd-467c-8b02-536c7dcfa311

Status: FAILURE

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[agones-bot]

Build Failed 😭

Build Id: 6282e303-2e50-42d0-8aed-2e69124d4dac

Status: FAILURE

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• Cloud Build log download

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[agones-bot]

Build Succeeded 🥳

Build Id: aea2c297-e638-4554-97d6-b95ed03836b4

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:1.61.0-dev-8e9b64c
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.61.0-dev-8e9b64c
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.61.0-dev-8e9b64c-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.61.0-dev-8e9b64c
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.61.0-dev-8e9b64c
• image: us-docker.pkg.dev/agones-images/ci/agones-processor:1.61.0-dev-8e9b64c
• Linux C++ SDK (build): agonessdk-1.61.0-dev-8e9b64c-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.61.0-dev-8e9b64c.zip

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

• https://8e9b64c-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4701/head:pr_4701 && git checkout pr_4701
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.61.0-dev-8e9b64c

[markmandel]

Question around docs.go (maybe a rename on the file?) - but approving - merge when you've worked out what you want to do about that nit.

[markmandel]

Loving how easy this is with the wrapper.

[agones-bot]

Build Succeeded 🥳

Build Id: 82a59d1d-1bc1-4fe3-b324-f140e2fc49e5

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:1.61.0-dev-a9cf5db
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.61.0-dev-a9cf5db
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.61.0-dev-a9cf5db-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.61.0-dev-a9cf5db
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.61.0-dev-a9cf5db
• image: us-docker.pkg.dev/agones-images/ci/agones-processor:1.61.0-dev-a9cf5db
• Linux C++ SDK (build): agonessdk-1.61.0-dev-a9cf5db-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.61.0-dev-a9cf5db.zip

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

• https://a9cf5db-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4701/head:pr_4701 && git checkout pr_4701
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.61.0-dev-a9cf5db