Create workflow for Z-phase calibration

[NoureldinYosri]

This calibration workflow is created for excitation preserving 2-qubit gates and assumes an error model that can be described with small random z-rotations

0: ───Rz(a)───two_qubit_gate───Rz(c)───
                │
1: ───Rz(b)───two_qubit_gate───Rz(d)───

for some small angles a, b, c, and d.

---

when the error model doesn't apply the workflow may give absured numbers (e.g. fidilities $\notin [0, 1]$). The fidilities can be slightly outside the $[0, 1]$ interval because it's a statistical estimate as can be seen in the following figure which compares the estimated fidelity of a CZ surrounded by random z rotations before and after calibration

test notebook: https://colab.sandbox.google.com/drive/10gZ5dggYKH_xSsCJFpg__GakxvoaZDIi

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.03960% with 4 lines in your changes missing coverage. Please review.

Project coverage is 97.83%. Comparing base (bb24dae) to head (87cb95a). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cirq-core/cirq/experiments/z_phase_calibration.py	89.65%	3 Missing :warning:
cirq-core/cirq/experiments/two_qubit_xeb.py	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6728 +/- ## ========================================== - Coverage 97.83% 97.83% -0.01% ========================================== Files 1077 1079 +2 Lines 92537 92659 +122 ========================================== + Hits 90535 90652 +117 - Misses 2002 2007 +5 ```

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