Use our own logic to go from ELECTRUM_VERSION to numeric android versionCode,
instead of using the default conversion done by python-for-android.
Even before this, we were already patching p4a to modify their logic (see [0]).
This commit changes that logic again, and moves it into a separate script in our repo.
- calculation change is due to the f-droid maintainers asking for the
arch code to be in the least significant digits (instead of most sig digits) (see [1])
I have pushed and changed to a new p4a branch, which is just a copy of the previous one
with 3 commits related to versionCode calc squashed.
[0]: edb7e4fe6d
[1]: https://github.com/spesmilo/electrum/issues/9210#issuecomment-2380559324
