testing/task3: new aport

https://taskwarrior.org
Command-line to-do list manager

This is version 3 of task, added as a new aport based on previous discussions.
https://github.com/GothenburgBitFactory/taskwarrior/releases/tag/v3.0.2

• Add post-install notice for version 2 users to export before using the new version
• Fix taskchampion timestamp build error for 32-bit arches
• Use newer ring version which fixes build error for ppc64le, riscv64, s390x

Based on patches from:

• termux packages
• Jan Christian Grünhage and nekopsykose

Update:

• task add, task list and task <id> done commands seem to be broken (partially for task add) on armv7. x86_64 is fine. Other arches untested.
• It should be possible to have the package use system corrosion and sqlite3 instead of vendor libs, but got a segfault during installation of the package when using system corrosion. (This is for corrosion 0.4.1-r0 as of current writing, corrosion upstream recently released 0.5.0.) Another patch will be needed to Cargo.lock to use system sqlite3.
• rust-lang/libc is updated to 0.2.155, and confirmed working for loongarch64 (thanks to znley).