feat(a380x/fma): disconnect ap for ldg message

[BravoMike99]

Fixes #[issue_no]

Summary of Changes

Adds the "DISCONNECT AP FOR LDG" FMA message on PFD.

Screenshots (if necessary)

References

Additional context

Discord username (if different from GitHub):
bruno_pt99

Testing instructions

1. Go to or below 150FT RA with one AP engaged with any of the following modes:
2. DES, OP DES, V/S or FPA (with 0 or negative value). The DISCONNECT AP FOR LDG message should appear on the PFD.
3. Fail the 3 RA systems through the EFB and make sure you have a landing airport inserted on the FMS.
4. Go to an altitude which is less or equal to the destination landing elevation +150FT with any of the modes mentioned in nr2. DISCONNECT AP FOR LDG message should appear once again (this one is easier to test with altimeter setting manipulation rather than having to fly close to the ground 😅 )
5. Disconnect autopilot after the FMA message is visible and it should disappear.
6. Fly an ILS approach and let the autopilot Autoland, the message should not appear.

How to download the PR for QA

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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

[tracernz]

.whenChanged is redundant, and we don't do Hungarian notation (that's the part I request mandatory changes for). I suggest some names like the following (also for additional clarity).

Suggested change

	private readonly radioHeightConsumer = ConsumerSubject.create(this.sub.on('chosenRa'), Arinc429Word.empty());
	private readonly altitudeConsumer = ConsumerSubject.create(this.sub.on('altitudeAr'), Arinc429Word.empty());
	private readonly landingElevation = ConsumerSubject.create(
	this.sub.on('landingElevation').whenChanged(),
	Arinc429Word.empty(),
	);
	private readonly ap1Consumer = ConsumerSubject.create(this.sub.on('ap1Active').whenChanged(), false);
	private readonly ap2Consumer = ConsumerSubject.create(this.sub.on('ap2Active').whenChanged(), false);
	private readonly verticalModeConsumer = ConsumerSubject.create(this.sub.on('activeVerticalMode').whenChanged(), 0);
	private readonly selectedVerticalSpeed = ConsumerSubject.create(this.sub.on('apVsSelected').whenChanged(), null);
	private readonly selectedFpa = ConsumerSubject.create(this.sub.on('selectedFpa').whenChanged(), null);
	private readonly approachCapabilityConsumer = ConsumerSubject.create(
	this.sub.on('approachCapability').whenChanged(),
	0,
	);
	private readonly radioHeight = ConsumerSubject.create(this.sub.on('chosenRa'), Arinc429Word.empty());
	private readonly altitude = ConsumerSubject.create(this.sub.on('altitudeAr'), Arinc429Word.empty());
	private readonly landingElevation = ConsumerSubject.create(
	this.sub.on('landingElevation'),
	Arinc429Word.empty(),
	);
	private readonly ap1Active = ConsumerSubject.create(this.sub.on('ap1Active'), false);
	private readonly ap2Active = ConsumerSubject.create(this.sub.on('ap2Active'), false);
	private readonly activeVerticalMode = ConsumerSubject.create(this.sub.on('activeVerticalMode'), 0);
	private readonly selectedVerticalSpeed = ConsumerSubject.create(this.sub.on('apVsSelected'), null);
	private readonly selectedFpa = ConsumerSubject.create(this.sub.on('selectedFpa'), null);
	private readonly approachCapability = ConsumerSubject.create(
	this.sub.on('approachCapability'),
	0,
	);