feat: Add gaussian quadrature integration option for initial sampling

[ConnorStoneAstro]

The sampling_mode can now be set to quad:x where x is an integer. AstroPhot will then begin sampling using gaussian quadrature. This is beneficial for small images where one may wish to avoid sub-pixel integration and simply define a good sampling depth right from the initial step.

[codecov[bot]]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (73e4109) 79.15% compared to head (72b17ff) 79.21%. Report is 21 commits behind head on dev.

Files	Patch %	Lines
astrophot/__init__.py	57.14%	3 Missing :warning:
astrophot/models/model_object.py	82.35%	3 Missing :warning:
astrophot/image/image_object.py	90.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #154 +/- ## ========================================== + Coverage 79.15% 79.21% +0.05% ========================================== Files 86 86 Lines 7186 7211 +25 ========================================== + Hits 5688 5712 +24 - Misses 1498 1499 +1 ```

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