Adds option to compress the size of RunContext (#7532)

- This allows the option to compress the size of RunContext by gzipping
the contents.
- From arbitrary tests, this can reduce the size of the RunContext by
about 10x.

For instance,
```
        sweeps = [
                cirq.Points(f'symbol_{num}',
                            [random.choice([0,-0.5,-1,0.5,1]) for _ in range(100)])
                            for num in range(100)]
        sweep = cirq.Zip(*sweeps)
        proto_compressed = v2.run_context_to_proto(sweep, 100, compress_proto=True)
        proto_uncompressed = v2.run_context_to_proto(sweep, 100, compress_proto=False)
        print(f'Compressed length: {len(proto_compressed.SerializeToString())}')
        print(f'Uncompressed length: {len(proto_uncompressed.SerializeToString())}')
```

Prints out:
```
Compressed length: 11807
Uncompressed length: 122606
```

Author: dstrain115

cirq-google/cirq_google/api/v2/run_context.proto

@@ -20,6 +20,10 @@ message RunContext {
   // If the same parameter is supplied in both places, the provision here in
   // device_parameters_override will have no effect.
   DeviceParametersDiff device_parameters_override = 2;
+
+  // If compression is desired, this field stores the gzipped bytes
+  // of the RunContext
+  bytes compressed_run_context = 3;
 }
 
 // Specifies how to repeatedly sample a circuit, with or without sweeping over

cirq-google/cirq_google/api/v2/run_context_pb2.py

@@ -14,6 +14,7 @@
 
 from __future__ import annotations
 
+import gzip
 import numbers
 from typing import Any, Callable, cast, TYPE_CHECKING
 
@@ -321,7 +322,11 @@ def metadata_from_proto(metadata_pb: run_context_pb2.Metadata) -> Metadata:
 
 
 def run_context_to_proto(
-    sweepable: cirq.Sweepable, repetitions: int, *, out: run_context_pb2.RunContext | None = None
+    sweepable: cirq.Sweepable,
+    repetitions: int,
+    *,
+    out: run_context_pb2.RunContext | None = None,
+    compress_proto: bool = False,
 ) -> run_context_pb2.RunContext:
     """Populates a RunContext protobuf message.
 
@@ -330,14 +335,23 @@ def run_context_to_proto(
         repetitions: The number of repetitions for the run context.
         out: Optional message to be populated. If not given, a new message will
             be created.
+        compress_proto: If set to `True` the function will gzip the proto and
+            store the contents in the bytes field.
 
     Returns:
         Populated RunContext protobuf message.
     """
     if out is None:
         out = run_context_pb2.RunContext()
+    if compress_proto:
+        uncompressed_wrapper = out
+        out = run_context_pb2.RunContext()
     for sweep in cirq.to_sweeps(sweepable):
         sweep_proto = out.parameter_sweeps.add()
         sweep_proto.repetitions = repetitions
         sweep_to_proto(sweep, out=sweep_proto.sweep)
+    if compress_proto:
+        raw_bytes = out.SerializeToString()
+        uncompressed_wrapper.compressed_run_context = gzip.compress(raw_bytes)
+        return uncompressed_wrapper
     return out

cirq-google/cirq_google/api/v2/run_context_pb2.pyi

@@ -14,6 +14,7 @@
 
 from __future__ import annotations
 
+import gzip
 import math
 from copy import deepcopy
 from typing import Iterator
@@ -417,6 +418,16 @@ def test_run_context_to_proto(pass_out: bool) -> None:
     assert out.parameter_sweeps[0].repetitions == 100
 
 
+def test_run_context_to_proto_with_compression() -> None:
+    sweep = cirq.Linspace('a', 0, 1, 21)
+    out = v2.run_context_to_proto(sweep, 100, compress_proto=True)
+    raw_bytes = gzip.decompress(out.compressed_run_context)
+    msg = v2.run_context_pb2.RunContext()
+    msg.ParseFromString(raw_bytes)
+    assert v2.sweep_from_proto(msg.parameter_sweeps[0].sweep) == sweep
+    assert msg.parameter_sweeps[0].repetitions == 100
+
+
 @pytest.mark.parametrize(
     'sweep',
     [