Fix handling of VEC_COND_EXPR trap tests [PR100284]

Fix handling of VEC_COND_EXPR trap tests [PR100284]

Now that VEC_COND_EXPR has normal unnested operands,
operation_could_trap_p can treat it like any other expression.

This fixes many testsuite ICEs for SVE, but it turns out that none
of the tests in gcc.target/aarch64/sve were affected.  Anyone testing
on non-SVE aarch64 therefore wouldn't have seen it.

gcc/
	PR middle-end/100284
	* gimple.c (gimple_could_trap_p_1): Remove VEC_COND_EXPR test.
	* tree-eh.c (operation_could_trap_p): Handle VEC_COND_EXPR rather
	than asserting on it.

gcc/testsuite/
	PR middle-end/100284
	* gcc.target/aarch64/sve/pr81003.c: New test.