Change the reverse behavior for various units

[Basilisk3]

Closes #5754

Outline of what is being done:

• Tracked and hover units will gain the ability to drive backwards
• Legged units will not get changed, as it looks odd and because most of them benefit less from the changes than other units (exceptions apply).
• Units that would gain a massive advantage from being able to move backwards will not be changed (e.g. the GC).

Planned BackUpDistances:

• Tech 4 units: 15
• Tech 3 units: 10
• Tech 2 units: 8
• Tech 1 units: 6

Stat changes

Megalith
BackUpDistance: 12 --> 15
MaxSpeedReverse: 50% of MaxSpeed (unchanged)

Scathis
BackUpDistance: 0 --> 15
MaxSpeedReverse: 0 --> 1.5 (same as MaxSpeed)

Othuum
BackUpDistance = 15 --> 10

All T3 Mobile Artilleries including the Suthanus
BackUpDistance: 0 --> 10
MaxSpeedReverse: 0 --> 2.2 (same as MaxSpeed)

Spearhead
BackUpDistance: 4 --> 10

T3 MAAs (only UEF and Seraphim)
BackUpDistance: 4 --> 10

All T2 MMLs
BackUpDistance: 4 --> 8
Give all MMLs the ability to reverse (Cybran, Aeon and Seraphim could not)

Pillar, Rhino and Obsidian
BackUpDistance: 0 --> 8
MaxSpeedReverse: 0 --> same as MaxSpeed

All T2 Hover Tanks, T2 Amphibious Tanks and the Absolver
BackUpDistance: 0 --> 8
BackUpDistance: 2 --> 8 (Yenzyne)
BackUpDistance: 0 --> 10 (Absolver)
MaxSpeedReverse: 0 --> same as MaxSpeed

All T2 Mobile Flaks
BackUpDistance: 0 --> 8
MaxSpeedReverse: 0 --> same as MaxSpeed

All Mobile Shields
BackUpDistance: 0 --> 8
BackUpDistance: 0 --> 10 (Athanah)
MaxSpeedReverse: 0 --> same as MaxSpeed

All T1 Artillieries
BackUpDistance: 0 --> 6
BackUpDistance: 2 --> 6 (Lobo)
MaxSpeedReverse: 0 --> same as MaxSpeed

Striker, Aurora and Thaam
BackUpDistance: 0 --> 6
MaxSpeedReverse: 0 --> same as MaxSpeed

Archer, Sky Slammer and Thistle
BackUpDistance: 0 --> 6
MaxSpeedReverse: 0 --> same as MaxSpeed

Snoop and Spirit
BackUpDistance: 2 --> 6
MaxSpeedReverse: 3.5 --> same as MaxSpeed (Spirit)

To-Do:

• Evaluate MaxSpeedReverse, it is the same as MaxSpeed for now.
• Evaluate if units without tracks should have a BackUpDistance, since it looks odd.

[Basilisk3]

This PR is ready for review. To not make this too convoluted, I decided to keep the unit's MaxSpeedReverse the same as their MaxSpeed. If this is deemed overpowered for some units, it can be changed accordingly. Let me know if you disagree, if necessary I can make a new PR specifically for the changes to MaxSpeedReverse.

[Garanas]

I'm going to wait with merging this until the next hotfix is out!

[Garanas]

@MrRowey the hotfix is not out yet, this should not have been merged.

[MrRowey]

My bad, In future can you add the do not merge tag so it's clear @Garanas