[cfloat.h] Add microscaling formats and typedefs for common floating point types

* Adds typedefs for commonly used floating point types.
* Adds a new header containing typedefs and implementations of Open
  Compute Microscaling formats.

Signed-off-by: Jerry Ge <jerry.ge@arm.com>
Change-Id: I0ad0e3c71e91d9e3af3b20d3a580b2ac52cdebec