Drop python 3.8 support after next pt release minor updates

[matteius]

Drop python 3.8 support after next pt release minor updates as its EOL now: https://devguide.python.org/versions/

Prerequisites:

• Fix the --system without --deploy flag bug #6297
• Vendor in pip==24.3.1 #6292
• Vendoring Fall 2024 #6293

Release 2024.3.1 with the above, let the dust settle a bit, and assuming no more break fix required, we drop 3.8

[oz123]

Release 2024.3.1 is already long ago done.