i2c-tools: change upstream and add python subpkg

[0x5c]

Things I am still unsure about:

• The subpackage name and short_desc
• How to ensure the subpackage's version is the version of the python module (it is versioned separately)

Closes #36156

Testing the changes

• I tested the changes in this PR: briefly
  • Distfile location change had no impact (same exact file as debian's)
  • Package builds fine and with the right files in the right place
  • Crossbuilds fine
  • Tested the python bindings

@leahneukirchen

[leahneukirchen]

You can't have a different version for a subpkg. Either make a new package, or just put it into the main package. Or use the "wrong" version.

[0x5c]

I decided that the version would simply be i2c-tools' version; since the version is only exposed in the module metadata inside i2c-tools' distfile, and since the distfile is versioned with i2c-tools' version, it would be an absolute mess to deal as a separate package.

I still have to fix crossbuilds and the python module building in the install phase, but I have a lead on that, just no testing time right now.

[0x5c]

The python module build happening in do_install has been fixed, but cross builds still have the problem where Python.h cannot be found.
However, the build succeeds if python3-devel is moved to hostmakedends, which doesn't seem right to me.

[0x5c]

All problems fixed, remains to test if it actually runs properly

[0x5c]

I was finally able to test this on a rpi1b

This is now ready for review