feat(a32nx/fws): Wire up APU generator faults

[FozzieHi]

Summary of Changes

This PR wires up the APU Generator failure we already have by adding the ELEC APU GEN FAULT master caution and APU GEN fault light. It does this by adding a APU GEN FAULT sim var written by the electrical system. In reality this should be written into discrete words by the EGIU, which should monitor the same outputs e.g. APU GEN line contactors (or GCU trips). We cannot do either of those at the moment as we don't have the EGIU modeled so I have added a TODO comment.

I have only done the A320 for now as the A380 electrical system is quite a bit more complex with more monitoring.

Screenshots (if necessary)

References

Very short flicker (150ms) of the APU GEN FAULT light on cold & dark start with just the APU:
https://youtu.be/bzKOdsusuQo?t=191

Additional context

Discord username (if different from GitHub): fozzie

Testing instructions

1. Have both engines running, start the APU normally, check that the FAULT light does not illuminate on the APU GEN pb
2. Trigger an APU Generator fault in the EFB, check that the FAULT light still does not illuminate on the APU GEN pb
3. Turn off an ENG GEN, check that the FAULT light illuminates on the APU GEN pb, and that the ELEC APU GEN FAULT master caution triggers after approximately 5 seconds

How to download the PR for QA

Every new commit to this PR will cause new A32NX and A380X artifacts to be created, built, and uploaded.

1. Make sure you are signed in to GitHub
2. Click on the Checks tab on the PR
3. On the left side, find and click on the PR Build tab
4. Click on either flybywire-aircraft-a320-neo, flybywire-aircraft-a380-842 (4K) or flybywire-aircraft-a380-842 (8K) download link at the bottom of the page