Fix MaximumInscribedCircle and LargestEmptyCircle performance and memory issues

[dr-jts]

This PR adds heuristics to MaximumInscribedCircle and LargestEmptyCircle to prevent long-running (and memory-intensive) processing for nearly flat and very thin inputs.

There are two problems solved:

1. if the input extent is very small in one dimension (i.e. almost flat), the cell grid was initialized with cells of very small size, causing a memory explosion. This is avoided by using a single initial grid cell covering the extent.
2. Very thin (low-area) geometries (or LEC boundaries) cause a long search to find a cell with a centre inside the geometry (since very few cells in the search space satisfy this condition). A heuristic is used to determine a maximum number of iterations permitted. This means that the computed result may lie outside the input geometry. This can be mitigated by using a smaller tolerance distance; but there is no way to guarantee the centre will lie inside.

This fixes the issue reported in libgeos/geos#875.