RISC-V: Refine test cases for both PR112929 and PR112988

RISC-V: Refine test cases for both PR112929 and PR112988

Refine the test cases for:

* Name convention.
* Add run case.

These test cases used to cause out-of-bounds writes to the stack
and therefore showed unreliable behavior.  Depending on the
execution environment they can either pass or fail.  As of now,
with the latest QEMU version, they will pass even without the
underlying issue fixed.  As the test case is known to have
caused the problem before we keep it as a run test case for
future reference.

	PR target/112929
	PR target/112988

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/vsetvl/pr112929.c: Moved to...
	* gcc.target/riscv/rvv/vsetvl/pr112929-1.c: ...here.
	* gcc.target/riscv/rvv/vsetvl/pr112988.c: Moved to...
	* gcc.target/riscv/rvv/vsetvl/pr112988-1.c: ...here.
	* gcc.target/riscv/rvv/vsetvl/pr112929-2.c: New test.
	* gcc.target/riscv/rvv/vsetvl/pr112988-2.c: New test.

Signed-off-by: Pan Li <pan2.li@intel.com>