Update scripts for metrics computation

[jonchang]

Description

Various updates needed to compute benchmark and metrics comparisons between tesseract and tr-ocr backends. In particular:

• Enabled comparing tesseract to tr-ocr for testing timing-based benchmarking
• Made the accuracy-based benchmarking actually run by fixing relative imports for the non-package install requirement of the /ocr folder
• Fix types of segments returned from segmentation functions (needs uint8, not int64)
• Use case-insensitive distance comparisons for metrics (tesseract can transcribe both caps and lowercase, unlike tr-ocr)
• Add tesseract options to the cli interface for accuracy-based benchmarking and update documentation accordingly

Rendered link for documentation updates

Related Issues

Part of #422

Checklist

• The title of this PR is descriptive and concise.
• My changes follow the style guidelines of this project.
• I have added or updated test cases to cover my changes.
• I've let the team know about this PR by linking it in the review channel

[jonchang]

Thanks @knguyenrise8!