Update table.py

[JorjMcKie]

These are important performance improvements for table handling:

Multiple standard methods in pymupdf's Rect class show grossly insufficient performance and slow down this module's work.
This is particularly true for rectangle containment and intersection checks.
We might consider re-assessing these places in PyMuPDF itself, but improving the table module is too urgent to wait. At first sight, the standard methods cover cases which may occur in a general context (e.g. also checking whether a Quad is contained in the rectangle), but not during table processing.

Other optimizations:
Multiple unnecessary extra text extractions have been replaced by look-ups in the character array (CHAR).