Documentation for public custom types is sourced in metadata of properties/methods that use them

[sbethur]

Description of issue

There are custom types that are accepted/returned by public methods:

• WaveformInfo by fetch, fetch_into, and read methods in niscope
• MeasurementStats by fetch_measurement_stats method in niscope
• HistoryRAMCycleInformation by fetch_history_ram_cycle_information method in nidigital
• LCRLoadCompensationSpot and LCRMeasurement (Soon-to-be-added methods in nidcpower will use these)

In the current code generator design, when generating the documentation for the properties/methods that use them, the docstring defined for the custom types are not used, but rather the docstring embedded in the metadata of the properties/methods are used. e.g.: Documentation for fetch: https://nimi-python.readthedocs.io/en/master/niscope/class.html#fetch (See the return value) The source for documentation: https://github.com/ni/nimi-python/blob/3dda150f74e9410693b198409c3b1e6f3cb32c22/src/niscope/metadata/functions.py#L1303

Drawbacks of current design:

• Creation and maintenance of the custom type documentation is cumbersome
• If the same type is used by multiple API, then we need to duplicate the documentation strings

[sbethur]

FYI @olsl21, your PRs - #1771 and #1772 will be impacted by this.