feat: add useq.WellPlanPlan widget with well selection

[tlambert03]

minimal working example of a plate selector extracted from @fdrgsp's code in #308

:joy:

TODO:

• [x] add back well names
• [x] support selection

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 98.01980% with 4 lines in your changes missing coverage. Please review.

Project coverage is 90.54%. Comparing base (370dfcd) to head (d8f76c1). Report is 29 commits behind head on main.

Files with missing lines	Patch %	Lines
...ymmcore_widgets/useq_widgets/_well_plate_widget.py	98.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #318 +/- ## ========================================== + Coverage 90.36% 90.54% +0.18% ========================================== Files 73 74 +1 Lines 8135 8336 +201 ========================================== + Hits 7351 7548 +197 - Misses 784 788 +4 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[tlambert03]

all yours @fdrgsp