Enhancement: Tidy the plotting library

[RHammond2]

This PR brings the entire openoa/utils/plot.py up to spec with later implemented best practices to ensure that figures can be customized in the methods to suit most needs for publication or presentation, or return the matplotlib objects back to add the final touches.

Given that plot_windfarm was added at a later point in time and is much cleaner, plot_array has been deprecated entirely. However, the following have been removed as a byproduct of their original intent being lost and their usage being unclear:

• plot_array
• subplot_powerRose_array
• powerRose_array
• subplot_c1_c2
• subplot_c1_c2_flagged
• subplot_c1_c2_raw_flagged
• subplt_power_curve
• turbine_polar_line
• turbine_polar_4Dscatter
• turbine_polar_contourf
• turbine_polar_contour

This PR closes #251.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 8.33333% with 22 lines in your changes missing coverage. Please review.

Project coverage is 65.50%. Comparing base (daf42ac) to head (371c4f2).

Files with missing lines	Patch %	Lines
openoa/utils/plot.py	8.33%	22 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop_v3 #253 +/- ## ============================================== + Coverage 61.85% 65.50% +3.64% ============================================== Files 29 29 Lines 4315 4061 -254 ============================================== - Hits 2669 2660 -9 + Misses 1646 1401 -245 ```

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