feat: add support for inplace getp

[AayushSabharwal]

Checklist

• [ ] Appropriate tests were added
• [ ] Any code changes were done in a way that does not break public API
• [ ] All documentation related to code changes were updated
• [ ] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [ ] Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[codecov[bot]]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (46070b2) 25.87% compared to head (8befb01) 26.38%.

Files	Patch %	Lines
src/parameter_indexing.jl	63.63%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #50 +/- ## ========================================== + Coverage 25.87% 26.38% +0.50% ========================================== Files 7 7 Lines 228 235 +7 ========================================== + Hits 59 62 +3 - Misses 169 173 +4 ```

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