feat(a32nx/fwc): Add brake low accu pressure master cautions

[FozzieHi]

Summary of Changes

Adds the BRK Y ACCU LO PR and PARK BRK LO PR master cautions. I wasn't able to find a perfect reference for the psi threshold. However, what I have found indicates 1650psi, and this matches a reference video below. Also cleanup some other parking brake logic.

Screenshots (if necessary)

Reference video

Sim

References

https://www.youtube.com/watch?v=cO-WX3FBQYw

Additional context

Discord username (if different from GitHub): fozzie

Testing instructions

1. Make sure the parking brake is off. Turn off the A/SKID & N/W STRG switch (to switch to the alternate braking system)
2. Turn off the HYD yellow ENG 2 pump, and PTU (to depressurise the yellow hydraulic system)
3. Apply and deapply toe brakes until the accumulator pressure gauge reads < 1650
4. Check that the BRK Y ACCU LO PR master caution triggers
5. Apply the parking brake, make sure that the BRK Y ACCU LO PR master caution is replaced with a PARK BRK LO PR master caution.

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.

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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