Add __repr__ for Numba and JAX linkers

Author: ricardoV94

pytensor/link/jax/linker.py

@@ -124,3 +124,6 @@ def create_thunk_inputs(self, storage_map):
             thunk_inputs.append(sinput)
 
         return thunk_inputs
+
+    def __repr__(self):
+        return "JAXLinker()"

pytensor/link/numba/linker.py

@@ -19,3 +19,6 @@ def jit_compile(self, fn_and_cache):
 
     def create_thunk_inputs(self, storage_map):
         return [storage_map[n] for n in self.fgraph.inputs]
+
+    def __repr__(self):
+        return "NumbaLinker()"