MAINT: avoid most of the warnings coming from dev CI

[martinfleis]

Some future-proofing, a lot of silencing. Got it down from 1200+ to 5, out of which 4 will be solved in upstream (apache/arrow#38374) and one seems to be coming from scipy.sparse internals, so there's not a lot we can do apart from silencing but I'd give it some time.

Closes #582

[jGaboardi]

Awesome. Great work.

[jGaboardi]

Approved too soon... Seeing failures – pandas._config.config.OptionError: No such keys(s): 'future.no_silent_downcasting'

[martinfleis]

Because the way pandas is deprecating the downcast keyword is not very friendly. You can either do that option, but that is available only on main or filter warnings. Given the behaviour in our case does not change, I will just filter them so they don't bubble up to a user.

[codecov]

Codecov Report

Merging #591 (781d8fa) into main (5d09bc6) will increase coverage by 0.2%.
Report is 1 commits behind head on main.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main    #591     +/-   ##
=======================================
+ Coverage   84.0%   84.2%   +0.2%     
=======================================
  Files        128     128             
  Lines      15053   15080     +27     
=======================================
+ Hits       12642   12698     +56     
+ Misses      2411    2382     -29     

Files	Coverage Δ
libpysal/cg/alpha_shapes.py	84.4% <100.0%> (+0.2%)	⬆️
libpysal/cg/tests/test_ashapes.py	97.4% <100.0%> (+0.2%)	⬆️
libpysal/graph/_utils.py	88.9% <100.0%> (+0.5%)	⬆️
libpysal/graph/base.py	96.4% <ø> (ø)
libpysal/io/iohandlers/pyDbfIO.py	78.0% <ø> (ø)
libpysal/io/iohandlers/tests/test_gwt.py	97.6% <100.0%> (+0.1%)	⬆️
libpysal/weights/tests/test_util.py	98.3% <100.0%> (ø)
libpysal/weights/util.py	78.5% <100.0%> (+1.5%)	⬆️

... and 2 files with indirect coverage changes