Support multi-document YAML files with yamldecode() (duplicate of #29729)

[shellwhale]

hashicorp/terraform#29729 was closed because manifest_decode_multi was added in the Kubernetes provider.

But not all yaml files are Kubernetes manifests ...

  │ Call to function "provider::kubernetes::manifest_decode_multi" failed:
  │ Invalid Kubernetes manifest: missing field "apiVersion".

Can we re-open the issue ?

My use case are Talos Linux machine configs

  │ Error: Error in function call
  │
  │   on talos-cluster-vsphere/main.tf line 27, in locals:
  │   27:     (provider::kubernetes::manifest_decode_multi(file(item))[0].machine.network.hostname) => provider::kubernetes::manifest_decode_multi(file(item))[0]
  │
  │ Call to function "provider::kubernetes::manifest_decode_multi" failed:
  │ Invalid Kubernetes manifest: missing field "apiVersion".