rhsm: move FactsImageOptions to the rhsm/facts package

Move the FactsImageOptions from distro to the new rhsm/facts package.
At the same time define the values we use as an enum, including the
"test-manifest" value.
Though the values don't really matter, the test value is defined first
so it takes the 0 value, which feels nicer conceptually.

The field in the distro.ImageOptions is changed to be a pointer to allow
for nil values.

internal/rhsm/facts/facts.go

@@ -0,0 +1,29 @@
+package facts
+
+import "fmt"
+
+type APIType uint64
+
+func (at APIType) String() string {
+	switch at {
+	case TEST_APITYPE:
+		return "test-manifest"
+	case CLOUDV2_APITYPE:
+		return "cloudapi-v2"
+	case WELDR_APITYPE:
+		return "weldr"
+	}
+	panic(fmt.Sprintf("invalid APIType value %d", at))
+}
+
+const (
+	TEST_APITYPE APIType = iota
+	CLOUDV2_APITYPE
+	WELDR_APITYPE
+)
+
+// The ImageOptions specify things to be stored into the Insights facts
+// storage. This mostly relates to how the build of the image was performed.
+type ImageOptions struct {
+	APIType APIType
+}