roachtest: tpcc: don't look at cloud during registration

This commit cleans up the tpcc code to not look at the cloud (leaked
through `TestSpec`) during registration. Instead, we define both GCE
and AWS values in the spec and decide between them when the test is
run.

Informs #104029
Release note: None

pkg/cmd/roachtest/cluster.go

@@ -2556,6 +2556,10 @@ func (c *clusterImpl) MakeNodes(opts ...option.Option) string {
 	return c.name + r.String()
 }
 
+func (c *clusterImpl) Cloud() string {
+	return c.spec.Cloud
+}
+
 func (c *clusterImpl) IsLocal() bool {
 	return config.IsLocalClusterName(c.name)
 }

pkg/cmd/roachtest/cluster/cluster_interface.go

@@ -108,6 +108,7 @@ type Cluster interface {
 
 	Spec() spec.ClusterSpec
 	Name() string
+	Cloud() string
 	IsLocal() bool
 	// IsSecure returns true iff the cluster uses TLS.
 	IsSecure() bool

pkg/cmd/roachtest/spec/cluster_spec.go

@@ -62,9 +62,13 @@ func (m MemPerCPU) String() string {
 // ClusterSpec represents a test's description of what its cluster needs to
 // look like. It becomes part of a clusterConfig when the cluster is created.
 type ClusterSpec struct {
-	Cloud        string
-	Arch         vm.CPUArch // CPU architecture; auto-chosen if left empty
-	InstanceType string     // auto-chosen if left empty
+	// TODO(#104029): We should remove the Cloud field; the tests now specify
+	// their compatible clouds.
+	Cloud string
+	Arch  vm.CPUArch // CPU architecture; auto-chosen if left empty
+	// TODO(radu): An InstanceType can only make sense in the context of a
+	// specific cloud. We should replace this with cloud-specific arguments.
+	InstanceType string // auto-chosen if left empty
 	NodeCount    int
 	// CPUs is the number of CPUs per node.
 	CPUs                 int