This bug is a regression of WL7200: that WL introduced an unconditional
recursive processing of AND and OR parse tree nodes during the
contextualization, when the original parser had some conditional
flattening of nested AND/OR expression.
That affected very long recursive AND/OR expression: instead of the normal
execution the parser failed with a parse error: ER_STACK_OVERRUN_NEED_MORE.

This bugfix re-introduces an optimization that flattens recursive AND/OR
expressions at parse time (before the itemization/contextualization):

 (X1 AND X2) AND (Y1 AND Y2) ==> AND (X1, X2, Y1, Y2)
 (X1 AND X2) AND Y ==> AND (X1, X2, Y)
 X AND (Y1 AND Y2) ==> AND (X, Y1, Y2)

and the same for OR.