Use custom exception when xyxymatch fails

[braingram]

Similar to: spacetelescope/tweakwcs#202

Both jwst and roman pipelines catch an exception that originates in this package:

stsci.stimage/src/immatch/xyxymatch.c

Line 67 in 14f9240

"Number of output coordinates exceeded allocation (%d)",

Using a custom exception (that subclasses RuntimeError to maintain backwards-compatibility) would allow the pipelines to catch this specific error without testing the error message.

[mcara]

Exception type is set here:

stsci.stimage/src/wrap/immatch/py_xyxymatch.c

Line 132 in 14f9240

PyErr_SetString(PyExc_RuntimeError, stimage_error_get_message(&error));

. IMO it is not worth the effort to modify this code to do string parsing here and defining custom exceptions in C code.