PPTX extractor

The batch upload pipeline depends on new extractors including the PPTX extractor. The PPTX extractor uses the python-pptx third-party component. The PPTX extractor uses python-pptx to extract slide-based chunks during DataLens Phase 2. The PPTX extractor implements slide-based chunking, with potential sub-slide splits for dense content. The PPTX extractor uses python-pptx to extract slide-based chunks during DataLens Phase 2. The PPTX extractor implements slide-based chunking, with potential sub-slide splits for dense content. The PPTX extractor operates via background workers to perform extraction tasks. The PPTX extractor capability is validated by the test_extractors test case.