fix(tcas): use correct altitudes

[tracernz]

Fixes #[issue_no]

Summary of Changes

Stops the TCAS erroneously going failed when the baro corrected altitude goes invalid, and fixes the slant range computation to use the appropriate value (PLANE ALTITUDE simvar from MSFS).

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub):

Testing instructions

Fail both FCUs, and ensure TCAS does not fault. Fail ADRs and ensure TCAS does fault:

• with air data switching knob in NORM or FO and ATC sys 1 selected and ADR 1 off,
• with air data switching knob in CAPT with ATC sys 1 selected and ADR 3 off,
• with air data switching knob in FO with ATC sys 2 selected and ADR 3 off,
• with air data switching knob in NORM or CAPT and ATC sys 2 selected and ADR 2 off.
  In the other combinations with the other two ADRs on the TCAS should be operational.

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

[BravoMike99]

Quality Assurance Tester Report

Discord Username : bruno_pt99
Object of testing : #9658
Aircraft : A32NX
Tier of Testing : 1
Date : 30/12/2024

Testing Process:
Failed both FCUs and verified no TCAS fault ✔️ .
With Air data selector in NORM or FO3 with ATC SYS & ADR 1 OFF/FAULT resulted in a TCAS fault ✔️
With air data selector in CPT & ATC SYS 1 & ADR 3 OFF/faulty a TCAS fault was generated ✔️ .
With air data selector in NORM OR FO3 & ATC SYS 2 & ADR3 OFF/faulty, the TCAS failed ✔️ .
With air data selector in NORM OR CPT3 & ATC SYS 2 & ADR2 OFF/faulty, the TCAS failed ✔️ .
With ATC SYS1, ADR2 OFF & ADR3 Operational -> No TCAS fault happened regardless of air data selector knob position✔️ .
With ATC SYS2, ADR1 OFF & ADR3 Operational -> No TCAS fault happened regardless of air data selector knob position ✔️ .

Testing Results:
Passed