dond to support time-dependence measurements (perhaps with ElapsedTimeParameter)

something like

```python
etp = ElapsedTimeParameter()
dond(etp, stuff_to_sweep_and_measure_here, ...)
```

first of all, `ElapsedTimeParameter` does not have a `set` method, so it can't be used in `dond` as an independent parameter. Secondly, the ask is to run a measurement until elapsed time is more than a specified value (e.g. until elapsed time is more than 10 minutes).

One quick workaround would be to use a dummy parameter as the `doNd` set parameter and include the `ElapsedTimeParameter` in the list of `meas_params`.

Originally requested by @guenp @samantha-ho

Start by reading the dond entry point and the ElapsedTimeParameter implementation, focusing on how independent parameters are set and how measurement loops terminate. Done should include support for elapsed-time-based stopping and a usable ElapsedTimeParameter in dond, while preserving the described measurement workflow.

Written by the indexing model from the issue text.