Implement Waveform

[GDYendell]

Needs work in pvi to open plots on a new display and configure axis range

[jsouter]

epics-containers/pvi#157

I was working on this in pvi this morning, just pushed onto my PR.
FastCS changes in scratch look like

            case Waveform():
                if (length := len(fastcs_datatype.shape)) == 2:
                    default_width = 800
                    height = int(
                        default_width
                        * fastcs_datatype.shape[0]
                        / fastcs_datatype.shape[1]
                    )
                    return ImageRead(
                        width=default_width, height=height, color_map=ImageColorMap.GRAY
                    )
                elif length == 1:
                    return ArrayTrace(axis="")
                else:
                    raise NotImplementedError(
                        f"Waveform shape {fastcs_datatype.shape} not supported"
                    )

Also tries to add XY trace support for edl, though that's disabled in FastCS right now anyway.

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.75%. Comparing base (9ebdf4d) to head (5b3bc92).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fastcs/transports/epics/pva/gui.py	87.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #247      +/-   ##
==========================================
- Coverage   90.83%   90.75%   -0.09%     
==========================================
  Files          70       70              
  Lines        2510     2519       +9     
==========================================
+ Hits         2280     2286       +6     
- Misses        230      233       +3     

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