Dynamically Apply OCR, Improve PDF Utilities and Tests

[JSv4]

Improve PDF utility tests

• test determination of whether pdf needs ocr
• Replace hardcoded temp paths with tempfile.TemporaryDirectory()
• fixed issue with function to split pdf into images - was not using proper file extensions.

Added a check to the nlm ingestor parsing step to dynamically apply OCR only where a pdf is NOT already OCRed.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.95238% with 4 lines in your changes missing coverage. Please review.

Project coverage is 71.44%. Comparing base (6f53378) to head (d972338). Report is 5 commits behind head on main.

Files	Patch %	Lines
opencontractserver/utils/pdf.py	78.94%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #167 +/- ## ========================================== + Coverage 70.44% 71.44% +1.00% ========================================== Files 59 59 Lines 2700 2718 +18 ========================================== + Hits 1902 1942 +40 + Misses 798 776 -22 ```

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