Add __repr__ for Numba and JAX linkers

Author: ricardoV94

pytensor/link/jax/linker.py

@@ -87,3 +87,6 @@ def create_thunk_inputs(self, storage_map):
             thunk_inputs.append(sinput)
 
         return thunk_inputs
+
+    def __repr__(self):
+        return "JAXLinker()"

pytensor/link/numba/linker.py

@@ -35,3 +35,6 @@ def create_thunk_inputs(self, storage_map):
             thunk_inputs.append(sinput)
 
         return thunk_inputs
+
+    def __repr__(self):
+        return "NumbaLinker()"