Send empty GKE objects explicitly

[modular-magician]

This change is mainly just to correct some currently misleading code- 2/3 of these fields are Computed and can't actually trigger this check (at least in reasonable circumstances) and linux_node_config still has a permadiff afterwards. This does mean that updates that remove linux_node_config that also include other changes will move on to the other changes so it at least has some user benefit, in addition to stopping the misleading snippet from propagating. This could be valid for some blocks, just not the one where is still happens!

Followup to GoogleCloudPlatform/magic-modules#11971

Release Note Template for Downstream PRs (will be copied)

container: `node_config.linux_config`, `node_config.workload_metadata_config` and `node_config.kubelet_config` will now successfully send empty messages to the API when `terraform plan` indicates they are being removed, rather than null, which caused an error. The sole reliable case is `node_config.linux_config` when the block is removed, where there will still be a permadiff, but the update request that's triggered will no longer error and other changes displayed in the plan should go through.

Derived from GoogleCloudPlatform/magic-modules#11978