Extract cirq-pasqal (quantumlib#4241)

Extracts cirq-pasqal as a separate module.

Merge after quantumlib#4239, a fix for json testing and deprecation warning deduping and quantumlib#4250, a fix for flnyt / minimal pytest dependencies (it contains them currently)

Author: balopat

cirq/__init__.py

@@ -580,7 +580,6 @@
 # Unflattened sub-modules.
 
 from cirq import (
-    pasqal,
     testing,
 )
 
@@ -622,6 +621,19 @@
     warning("Can't import cirq_ionq: ", exc_info=ex)
 
 
+try:
+    _compat.deprecated_submodule(
+        new_module_name='cirq_pasqal',
+        old_parent=__name__,
+        old_child='pasqal',
+        deadline="v0.14",
+        create_attribute=True,
+    )
+except ImportError as ex:
+    # coverage: ignore
+    warning("Can't import cirq_pasqal: ", exc_info=ex)
+
+
 def _register_resolver() -> None:
     """Registers the cirq module's public classes for JSON serialization."""
     from cirq.protocols.json_serialization import _internal_register_resolver

cirq/json_resolver_cache.py

@@ -108,8 +108,6 @@ def two_qubit_matrix_gate(matrix):
         '_PauliY': cirq.ops.pauli_gates._PauliY,
         '_PauliZ': cirq.ops.pauli_gates._PauliZ,
         'ParamResolver': cirq.ParamResolver,
-        'PasqalDevice': cirq.pasqal.PasqalDevice,
-        'PasqalVirtualDevice': cirq.pasqal.PasqalVirtualDevice,
         'ParallelGateOperation': cirq.ParallelGateOperation,
         'PauliString': cirq.PauliString,
         'PhaseDampingChannel': cirq.PhaseDampingChannel,
@@ -130,12 +128,10 @@ def two_qubit_matrix_gate(matrix):
         'SwapPowGate': cirq.SwapPowGate,
         'SymmetricalQidPair': cirq.SymmetricalQidPair,
         'TaggedOperation': cirq.TaggedOperation,
-        'ThreeDQubit': cirq.pasqal.ThreeDQubit,
         'Result': cirq.Result,
         'Rx': cirq.Rx,
         'Ry': cirq.Ry,
         'Rz': cirq.Rz,
-        'TwoDQubit': cirq.pasqal.TwoDQubit,
         'TwoQubitMatrixGate': two_qubit_matrix_gate,
         '_UnconstrainedDevice': cirq.devices.unconstrained_device._UnconstrainedDevice,
         'VarianceStoppingCriteria': cirq.work.VarianceStoppingCriteria,