Improve Serialization performance in Cirq

[tanujkhattar]

Summarize the task
The Json serialization was not designed to be compact or fast. Benchmarks for json serialization, added in #5957, show that it takes O(seconds) to serialize a (1000 qubit, 100 moment) circuit containing one and two qubit gates. We want this number to be O(milliseconds). To make this happen, see whether:

• We can improve the performance of serialization/deserialization using the existing json serialization data model.
• If not, design a new serialization model with better performance scaling.

The current json serialization framework is described in https://quantumai.google/cirq/dev/serialization

Part of: #6097

[navaro1]

I'd like to work on this one

[JayPankajPatel]

I'd like to work on this issue

[navaro1]

As I first step, I will benchmark orjson in as simple as possible way to see if we can consider staying within JSON model.

orjson is considered most performant (and it is also well grounded) library for python json serialisation, hence the choice.

[navaro1]

After very initial investigation, orjson seems like agood place to start. My goal is to have < 150 ms for 1000 qubit, 100 moment performance check. I'll prepare draft PR as a starting point for discussion.