Move EXCEPTION_ENABLE_SUPPORTED out of math-tests.h.

Continuing moving macros out of math-tests.h to smaller headers
following typo-proof conventions instead of using #ifndef, this patch
moves the EXCEPTION_ENABLE_SUPPORTED macro out to its own
math-tests-trap.h header.

Tested with build-many-glibcs.py.

	* sysdeps/generic/math-tests-trap.h: New file.
	* sysdeps/generic/math-tests.h: Include <math-tests-trap.h>.
	(EXCEPTION_ENABLE_SUPPORTED): Do not define here.
	* sysdeps/aarch64/math-tests.h: Remove file.
	* sysdeps/arm/math-tests.h: Likewise.
	* sysdeps/riscv/math-tests.h: Likewise.
	* sysdeps/aarch64/math-tests-trap.h: New file.
	* sysdeps/arm/math-tests-trap.h: Likewise.
	* sysdeps/riscv/math-tests-trap.h: Likewise.