Moving to numba=0.53.1

[kozlov-alexey]

Motivation: keep up with latest Numba release.

Note: commit 2017e6c is actually just a workaround for numba=0.53.1 regressions and probably should be reverted once referred issues are fixed.

[kozlov-alexey]

Regarding possible performance impact for numpy_like.astype() from numeric arrays to StringArrayType. There's actually no impact at all, since for some reason iterating over StringArrayType with prange doesn't scale (should be investigated), so testing conversion from 5 * 10 ** 6 of int64 to string, SDC code is 1.5x times faster than pandas, but doesn't scale (i.e. with and without this change):

n_threads	1	2	4	8	16
tested	1.769644	1.77148	1.768676	1.768381	1.769647
reference	2.677486	2.624062	2.624959	2.622924	2.625067
ratio	1.513008	1.481282	1.484138	1.483235	1.483385

[kozlov-alexey]

Numba=0.53.1 regressions mentioned above are: numba/numba#6969 and numba/numba#6960