improve code pythonic readability

[fametrano]

While at https://github.com/bitcoin-core/HWI/pull/409 and https://github.com/bitcoin-core/HWI/pull/410 I just couldn't resist to try and improve some pythonic readability.

Namely, I

• converted for loop into call to sum()
• inlined variable that is immediately returned
• lifted return into if
• merged duplicate blocks in conditional, removing redundant conditional
• replaced unused for index ('txout') with underscore
• replaced if statement with if expression
• replaced multiple comparisons of same variable with in operator
• replaced unneeded comprehension with generator
• simplified if expression by using or
• simplified conditional into return statement
• used any() instead of for loop, inverted any/all to simplify comparisons

As I know stylistic PR are not welcome, let me stress here that modern python coding should leverage mypy, black, flake8, pylint, bandit, isort, and sourcery. These tools combined provide a powerful contribution, helping your residual bug not to be lost among hundreds of warnings.

This PR includes https://github.com/bitcoin-core/HWI/pull/409 but could be made independent from it; if both PRs are accepted, it should be merged later to separate the functionality change from the cosmetic changes.

If this is rejected... well I got some fun :-) and, actually, the relevant PR is really https://github.com/bitcoin-core/HWI/pull/410