Consolidate codegen and JIT modules.

Consolidate all code-generation related front-end APIs into pystencils.codegen module. Consolidate all JIT-related front-end APIs into pystencils.jit.

First part of #116 (closed).

pystencils.codegen

The codegen module consolidates target, config, kernelcreation, backend.properties and backend.kernelfunction. It is home to the code generation drivers, their configuration, invocation APIs, and output objects. The drivers internally invoke the backend; backend APIs are now no longer exposed to the user (apart from some exceptions).

pystencils.jit

The jit module is moved out of backend (where it never really belonged). It shall be the home of all JIT-related APIs and functionality.

src/pystencils/inspect.py

-from dataclasses import dataclass
-from typing import ClassVar
-
 from .backend.ast import PsAstNode
 from .backend.emission import CAstPrinter, IRAstPrinter, EmissionError
 
@@ -84,50 +81,74 @@ class AstInspection:
         return html_code
 
 
-@dataclass
+class IntermediateAst:
+    def __init__(self, description: str | None = None):
+        self._description = description
+        self._name: str
+        self._lookup: str
+
+    @property
+    def description(self) -> str:
+        if self._description is not None:
+            return self._description
+        else:
+            return self._name
+
+    def __set_name__(self, owner, name: str):
+        self._name = name
+        self._lookup = f"_{name}"
+
+    def __get__(self, obj, objtype=None) -> AstInspection | None:
+        if obj is None:
+            return None
+
+        ast = getattr(obj, self._lookup, None)
+        if ast is not None:
+            return AstInspection(ast)
+        else:
+            return None
+
+    def __set__(self, obj, val: PsAstNode | None):
+        setattr(obj, self._lookup, val)
+
+
 class IntermediatesInspection:
     """Inspect intermediate results produced by the code generator."""
 
-    parsed_body: PsAstNode | None = None
-    materialized_ispace: PsAstNode | None = None
-    constants_eliminated: PsAstNode | None = None
-    cpu_canonicalize: PsAstNode | None = None
-    cpu_hoist_invariants: PsAstNode | None = None
-    cpu_vectorize: PsAstNode | None = None
-    cpu_select_intrins: PsAstNode | None = None
-    cpu_openmp: PsAstNode | None = None
-    lowered: PsAstNode | None = None
-
-    DESCR: ClassVar = {
-        "parsed_body": "Freeze & Type Deduction",
-        "materialized_ispace": "Iteration Space Materialization",
-        "constants_eliminated": "Constant Elimination",
-        "cpu_canonicalize": "CPU: Symbol Canonicalization",
-        "cpu_hoist_invariants": "CPU: Hoisting of Loop Invariants",
-        "cpu_vectorize": "CPU: Vectorization",
-        "cpu_select_intrins": "CPU: Intrinsics Selection",
-        "cpu_openmp": "CPU: OpenMP Instrumentation",
-        "lowered": "C Language Lowering",
-    }
+    parsed_body: IntermediateAst = IntermediateAst("Freeze & Type Deduction")
+    materialized_ispace: IntermediateAst = IntermediateAst(
+        "Iteration Space Materialization"
+    )
+    constants_eliminated: IntermediateAst = IntermediateAst("Constant Elimination")
+    cpu_canonicalize: IntermediateAst = IntermediateAst("CPU: Symbol Canonicalization")
+    cpu_hoist_invariants: IntermediateAst = IntermediateAst(
+        "CPU: Hoisting of Loop Invariants"
+    )
+    cpu_vectorize: IntermediateAst = IntermediateAst("CPU: Vectorization")
+    cpu_select_intrins: IntermediateAst = IntermediateAst("CPU: Intrinsics Selection")
+    cpu_openmp: IntermediateAst = IntermediateAst("CPU: OpenMP Instrumentation")
+    lowered: IntermediateAst = IntermediateAst("C Language Lowering")
 
     def _ipython_display_(self):
         from IPython.display import display
         import ipywidgets as widgets
 
-        from dataclasses import fields, asdict
-
-        all_fields = fields(IntermediatesInspection)
-        fields_dict = asdict(self)
-
-        all_asts = [
-            (self.DESCR.get(f.name, f.name), fields_dict[f.name])
-            for f in all_fields
-            if fields_dict[f.name] is not None
+        all_fields = [
+            (name, obj.description)
+            for name, obj in IntermediatesInspection.__dict__.items()
+            if isinstance(obj, IntermediateAst)
         ]
 
-        labels = [t[0] for t in all_asts]
+        previews: list[AstInspection] = []
+        labels: list[str] = []
+
+        for name, descr in all_fields:
+            preview = getattr(self, name)
+            if preview is not None:
+                previews.append(preview)
+                labels.append(descr)
 
-        code_views = [AstInspection(t[1])._widget() for t in all_asts]
+        code_views = [p._widget() for p in previews]
 
         select_label = widgets.HTML("<div><b>Code Generator Stages</b></div>")
         select = widgets.Select(options=labels)