ECL crash with Hermite polynomials

[rws]

sage: %time _=hermite(10000,x)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
RuntimeError: ECL says: Memory limit reached. Please jump to an outer pointer, quit program and enlarge the
memory limits before executing the program again.

There is no reason for this because coefficients can be computed directly using big integers:

sage: %time _= [factorial(10000)/(factorial(k)*factorial(10000-2*k)) for k in range(1,5000)]
CPU times: user 4.33 s, sys: 24 ms, total: 4.35 s
Wall time: 4.32 s

A Pynac prototype is about 50x faster than Maxima for expression creation and creates H_10000 in 670ms.

[rws]

Fixed in #20312.