Use appropriate buffer for QgsGeometry::XXXContainedInLine. Fix #10999.

We have reduced the problem by reducing the size of the buffer used in QgsGeometry::XXXContainedInLine functions.
The error may still occur depending on:
   the accuracy of the projection used,
   the distance between the object to modify and the nearest point.
So we caught the error, stop capturing and displaying a more specific message.
Are you sure this is correct?
For big coordinates (order of millions) this would be 0.1 ** (6-1) = 0.00001
For small coordinates (order of tens) this would be 0.1 ** (1-1) = 0.1
Shouldn't that be reversed - or am I missing something?