feat: Add ROI selection to stage explorer, and scan button to scan selected ROI

[fdrgsp]

Untitled.mov

[codecov]

Codecov Report

Attention: Patch coverage is 46.17647% with 183 lines in your changes missing coverage. Please review.

Project coverage is 89.06%. Comparing base (c4b863d) to head (65bf77f).

Files with missing lines	Patch %	Lines
.../pymmcore_widgets/control/_stage_explorer/_rois.py	36.81%	127 Missing ⚠️
...widgets/control/_stage_explorer/_stage_explorer.py	54.78%	52 Missing ⚠️
...e_widgets/control/_stage_explorer/_stage_viewer.py	83.33%	4 Missing ⚠️

❌ Your patch check has failed because the patch coverage (46.17%) is below the target coverage (85.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #428      +/-   ##
==========================================
- Coverage   90.53%   89.06%   -1.48%     
==========================================
  Files          90       91       +1     
  Lines        9850    10150     +300     
==========================================
+ Hits         8918     9040     +122     
- Misses        932     1110     +178     

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[tlambert03]

i made some additional cleanups on ROI. Next thing I see that we should do is here: we should pass the canvas position into the creation of the ROIRectangle, so that the very first place that the handles are positioned is correctly in world space. (i.e. "please create an ROIRectangle at this position`), to avoid a flash of seeing the handles at the origin, and then quickly moving them when the mouse drags

[tlambert03]

did a number of updates here, added an ROI manager, and a "scan selected ROI" button. movie added to original post