Notebook: ParameterWithSetpoints for buffered sweep

[jenshnielsen]

An example of how buffered sweep could be done with parameter with setpoints

[codecov]

Codecov Report

Merging #2263 into master will not change coverage.
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[astafan8]

The more use-case-driver tutorials - the better :)

Remarks:

• the notebook lacks description of what it tries to explain, it seems like only people who requested this example will understand it :( Could we a bit more description to the top of the notebook?
• i think the notebook will read better if DummyArray class is not there, and ParameterWithSetpoints is used explicitly.
• it's unclear why one would change the setpoints of PwS on the DMM, there's a cell saying "or even change it".