fix: Improve OCR results, stricten criteria before dropping bitmap areas

[cau-git]

This introduces multiple changes to address problems with partially failing content in scanned documents.

• The code for detection of OCR rectangles now merges almost-connected, nearby bitmap rectangles into one
• OCR rectangles are not dropped individually if they don't pass the size threshold, only if the sum of all OCR rectangles falls below the size threshold
• EasyOCR confidence lowered to 0.5 (from 0.65) for better recall

Issue resolved by this Pull Request:
Resolves #641 and others

Checklist:

• Documentation has been updated, if necessary.
• Examples have been added, if necessary.
• Tests have been added, if necessary.

[mergify]

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[dolfim-ibm]

LGTM

[nikos-livathinos]

Looks good to me.