feat: anthos modules remote fleet project

[CPL-markus]

It should be possible to enable the ACM feature on a GKE cluster that has its fleet in a separate project.

Therefore an additonal variable hub_project_id was introduced to reference the fleet project id. If it is empty (default), the project_id variable will be used instead.

[CPL-markus]

@apeabody Sorry, messed up the old pull-request (#1981) while trying to patch something in Git. Please check this (new) request again.

[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @CPL-markus!

        	Error:      	Received unexpected error:
        	            	FatalError{Underlying: error while running command: exit status 1; 
        	            	Error: Failed to retrieve project, pid: , err: project: required field is not set
        	            	
        	            	  with module.example.module.acm.google_gke_hub_feature.acm[0],
        	            	  on ../../../modules/acm/feature.tf line 17, in resource "google_gke_hub_feature" "acm":
        	            	  17: resource "google_gke_hub_feature" "acm" {
        	            	}
        	Test:       	TestSimpleZonal

[CPL-markus]

My bad, the evaluation of empty strings seems to require coalesce, instead of try to ensure the right variable is used.

[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @CPL-markus!

[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @CPL-markus!

[apeabody]

@CPL-markus - Can you please rebase/merge? Thanks!

[CPL-markus]

@apeabody I rebased it, but merging is blocked as I need your help in running the pipeline again. :-)

[apeabody]

/gcbrun