collection of small fixes, features, and random pieces of code

[hay-k]

This PR brings the following:

• some cherry picked commits from branch alvaro/latest_20231215 that collectively
  1. introduce support for couplers in the qblox driver.
  2. expose offset_i and offset_q mixer calibration parameters for qblox RF modules.
• cleanup of the said commits to
  1. align the code with main (the commits were based on older version of qibolab)
  2. make the code more pythonic and more readable
  3. remove things that were done from a perspective of a user that uses qblox alone (i.e. from a perspective where qibolab==qblox driver), but should not be part of things qibolab does.
• fix "deserialization" of Custom pulse shape:
  • as a side effect fixes deserialization of IIR, and SNR as well.

This is intended to cover the discussions in https://github.com/qiboteam/qibolab/issues/919 and https://github.com/qiboteam/qibolab/issues/921