New packages: python3-{cloup,deepmerge,packageurl-python} & python3-boltons update

[kdeldycke]

Summary

This PR adds 3 new Python packages that Void does not ship yet, as well as an update for one existing package (simplifying python3-boltons). Each change has its own commit.

The python3-boltons package being orphaned, I proposed to take over its maintenance.

None of these are my own libraries.

Testing the changes

• I tested the changes in this PR: YES

Built each on a Void x86_64 VM against master with ./xbps-src -Q pkg.

xlint reports nothing for any of the four templates.

New package

• This new package conforms to the package requirements: YES

Local build testing

• I built this PR locally for my native architecture, (x86_64-glibc)
• I did not build it for other architectures: all packages are pure Python and ship no compiled code.

Context

This work has been initially proposed as part of the #60532 PR, in which I packaged my own project. This being strictly forbidden by the contribution guidelines, I extracted the work I did on dependencies I am not an author of. This salvaged the part that strictly respects the guidelines so this can still benefits the community. And as a gesture of good will, I took the liberty to adopt the python3-boltons orphaned package.