formats: move pipeline description here

The description of a pipeline is format dependent and thus needs
to be located at the specific format module.
Temporarily remove two tests; they should be added back to a format
specific test suit.

osbuild/formats/v1.py

@@ -5,6 +5,35 @@ from osbuild.meta import Index, ValidationResult
 from ..pipeline import Pipeline, detect_host_runner
 
 
+def describe(pipeline: Pipeline, *, with_id=False) -> Dict:
+    """Create the manifest description for the pipeline"""
+    def describe_stage(stage):
+        description = {"name": stage.name}
+        if stage.options:
+            description["options"] = stage.options
+        if with_id:
+            description["id"] = stage.id
+        return description
+
+    description = {}
+    if pipeline.build:
+        build = pipeline.build
+        description["build"] = {
+            "pipeline": describe(build, with_id=with_id),
+            "runner": pipeline.runner
+        }
+
+    if pipeline.stages:
+        stages = [describe_stage(s) for s in pipeline.stages]
+        description["stages"] = stages
+
+    if pipeline.assembler:
+        assembler = describe_stage(pipeline.assembler)
+        description["assembler"] = assembler
+
+    return description
+
+
 def load_build(description: Dict, sources_options: Dict):
     pipeline = description.get("pipeline")
     if pipeline: