Enhancement: Add retry logic to gcom plugin publishing

[briangann]

originally open here https://github.com/grafana/grafana-community-team/issues/486

I deployed polystat to prod, which did all 3 environments, but dev gcom failed with this:

https://github.com/grafana/grafana-polystat-panel/actions/runs/16352995196/job/46204821501

Publishing to https://grafana-dev.com/api
{
  "download": {
    "any": {
      "url": "https://redacted/grafana-polystat-panel/release/2.1.15/any/grafana-polystat-panel-2.1.15.zip"
    }
  },
  "url": "https://github.com/grafana/grafana-polystat-panel",
  "commit": "96d99e762eb2a5cdbab157baad9ab99cfac0f19b",
  "scopes": [
    "universal"
  ]
}
Response:
{
  "code": "InvalidArgument",
  "message": "Plugin with this version already exists. Please use a new version number.",
  "requestId": "4a3b32fa-65f1-4dcb-aa48-8c3eb362e019"
}
Plugin version already exists; IGNORE_CONFLICTS=true so treating as success

It did however succeed to publish, but the whole CD pipeline stopped and didn't proceed with the release in github.

https://grafana-dev.com/api/plugins/grafana-polystat-panel/versions/2.1.15

We could add some retry logic - if gcom fails, check if it really was accepted and call it a success)