Generic Math.md: Refactor onto single type hierarchy.

[otac0n]

Batch of updates to the Generic Math.md proposal as discussed in chat.

Summary of the PR

• During the implementation, I found the integer version of Matrix.Lerp could not be reasonably implemented.
• Extension methods should be used for the public API per the chat.
• The types can be unified by eliminating the properties and bitwise operators.

Related issues, Discord discussions, or proposals

https://discord.com/channels/521092042781229087/587346162802229298/1378782513010577449 and prior

Further Comments

Partially implemented in #2459

[Perksey]

It's probably worth clarifying at line 23 what our intention is i.e. using one type with extension APIs (and replacing all usages of VectorNF/VectorNI with VectorND as necessary)

[Perksey]

Very minor comments

[Perksey]

• It's weird having instance invocations (extension methods) and static methods.
  • Should we follow System.Numerics where possible?
  • Should we use this for things that would otherwise be an infix operator only?
  • We will remove instance extension methods and add them back later if we still want them.
  • We visited Length/LengthSquared as properties instead of .NET
• Approved notwithstanding instance extension method and Atan2(Memberwise, Scalar) removal