Investigate how we can extend `Dimension` to keep track of the function to generate points

[coretl]

We require the following:

• For motors:
  • For step scan: the midpoints of the entire scan
  • For PVT fly scans: to know if a contiguous section is linear, then time interpolated positions for the section
  • For servo rate fly scans: time interpolated positions for each contiguous section
• For detectors: the number of frames, min and max duration for the scan
• For triggering:
  • For position collection window: the lower bound of each contiguous section
  • For position frames: the lower bound of each frame
  • For time frames: the duration of each frame in a contiguous section

To do this, we require #167, then some ability for Specs to publish whether they are linear, and the function that should be used to generate interpolated points. I suggest that we still generate midpoints up front, but upper and lower bounds could be generated from the function.

There is still an open question as to what time interpolated points look like when the total duration of the contiguous section is not a multiple of the time period, should it truncate, extend, or stretch the time?

Acceptance Criteria

• A proposal of how to extend Path and Dimension to allow this