Units API Rewrite

[narmstro2020]

So this PR is based on feedback and discussion from PR #6710, #6696, #6684, #6676

I know some of those are mine. I will consider those dead and will leave them only for references to the feedback and notes.

I'm going to start with taking the existing units API and breaking it down into separate measurement type packages, angle, time, dimensionless, angularvelocity, etc.

Each will have an a class equivalent to the old Measure interface and ImmutableMeasure class which will handle immutable measures. (i.e. Angle)

Each will have a class that will handle the units of that type (i.e. AngleUnit)

Each class that handles Immutable measures will have a child class that handles mutable ones (i.e. MutableAngle).

At first (and probably at the end) many of the packages will be near duplicates of each other except for minor variations to handle division, multiplication, etc.

For the most part no generics will be used. They might come back in a limited form as this is further optimized, but no guarantees.

Every unit of a certain measurement type will have all of its derived units go back to the S.I. standard unit. As an example feet will be based on meters and inches will be based on meters. New units will not be based off of other ones unless that other one is the S.I. base (or derived as in the case of m/s). I've found it confusing when seeing the word base in the old API and not knowing if S.I. base or a unit that a new one is based on is used.

Units that are derived from the standard S.I. base units will be done so here as well much like the way AngularVelocity is done.

I'll not be focusing on UnitBuilder at this time. I'll effectively deprecate it. Though custom units of a type can still be created through the constructors and static methods of that type.

Of course feeback is welcome. I'll leave this in draft form until I've effectively replaced all of the existing units with the new setup.