Remove unneeded start parameter of zero from Python range function #13220

This removes the default first parameter of zero from Python range functions when it's not needed.

https://docs.python.org/3.5/library/stdtypes.html#range

The majority of the codebase uses the range without the zero as the first parameter.

I used a regex in PyCharm to just search through Python files for the range functions that I changed in this PR. Regex was -> range *\( *0

The only other results are the range functions that use all three parameters, start - stop - step.

The changes look correct, but according to the guidelines I have to close this (c.f. the section on refactoring https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md#refactoring)

Generally, if the style is not mentioned and fixed in the developer notes, we leave it up to the original author to pick whatever fits them best personally and then leave it that way until the line is touched for other reasons.

If you are looking for small things to help out with, you can

• search through the good first issues or the ones that are up for grabs.
• write tests to improve the coverage (both unit tests and rpc tests are welcome)
• help with review and testing (There are easy ones such as the gui and rpc)
• join us on irc and let us know what you are interested in.

Hey @MarcoFalke I understand. Would adding a new Python Flake 8 check be something that was valued as pull request ?

They are already handled in #13214. Feel free to leave a comment there.

Also, an initial zero in the range is helpful for clarity, even if it is not strictly necessary for the actual function.