Spin gen enums

[Christian-B]

Based on changes made in
https://gitlab.com/spinnaker2/SpiNNMachine2/-/blob/main/spinn_machine/version/version_factory.py

Create SPIN1_GEN and SPIN2_GEN enums to clearler show where the versions come from.

Changes to how SpiNNcloud did it.

1. Classes SPIN1_GEN and SPIN2_GEN moved to their own py files
2. Standalone constants THREE, FIVE, SPIN2_1CHIP, SPIN2_48CHIP completely removed
3. when used in set_config wrapped in a str function for typing

• note: it needs to be str(Spin2Gen.SPIN2_1CHIP.value) and not just str(Spin2Gen.SPIN2_1CHIP) for python 3.10

Must be done at the same time as SpiNNakerManchester/PACMAN#635 (or an alternative)

[rowleya]

Apologies, I approved this thinking it was part of the parameterized, but I think this one is in conflict, so probably should be closed instead.