Drop the ClassVarMeta/metaclass/ABCMeta stuff -- it doesn't seem to
serve any purpose that is not similarly achieved with plain python
inheritance.
Upcoming patches will use normal inheritance a lot more.
Note that most use of the ClassVarMeta was in the SdKey subclasses, and
that these currently don't actually work. See the fix in patch
I07dfc378705eba1318e9e8652796cbde106c6a52 .
name: set a default name from the python class, as ClassVarMeta did.
Also allow setting an explicit string as name instead, per subclass
implementation (see I31f390d634e58c384589c50a33ca45d6f86d4e10).
Related: SYS#6768
Change-Id: I60ea8fd11fb438ec90ddb08b17b658cbb789c051
8e6a19d9f0