The public libraries are more trustworthy than third-party libs when it comes to security.
See https://docs.python.org/3/library/secrets.html
This is a partial backport of electrum#5947
https://github.com/spesmilo/electrum/pull/5947/commits/004acb906d33ea3a13c87b7b05c67a33e1d3e3d9: ecc: abstract away some usage of python-ecdsa: randrange
and
https://github.com/spesmilo/electrum/commit/120da2783b032be0a58d01c1ef40a23dcff88f2b: util.randrange: use stdlib 'secrets' module instead of 'python-ecdsa'
https://github.com/spesmilo/electrum/commit/2c2e3f8ca40b97c9959b5e424cbf69cde53384cf: util.randrange: expand docstring
Depends on D16664