python: Remove inline context

Instead of encoding the entire context and context decoder in the python
bindings, capture the compacted versions of each string at code
generation time and pass them to the encoder/decoder

src/shacl2code/lang/templates/jsonschema.j2

@@ -61,10 +61,10 @@
             "allOf": [
                 {
                     "properties": {
-                        "{{ class.id_property or context.compact("@id") }}": { "$ref": "#/$defs/{{ class.node_kind.split("#")[-1] }}" },
+                        "{{ class.id_property or "@id" }}": { "$ref": "#/$defs/{{ class.node_kind.split("#")[-1] }}" },
                         "{{ context.compact("@type") }}": { "const": "{{ context.compact_vocab(class._id) }}" }
                     }{%- if class.node_kind == SH.IRI %},
-                    "required": ["{{ class.id_property or context.compact("@id") }}"]
+                    "required": ["{{ class.id_property or "@id" }}"]
                     {%- endif %}
                 },
                 { "$ref": "#/$defs/{{ varname(class.clsname) }}_props" }