[frameworks][native][vulkan] fix -Walloca

Alloca cannot be checked for failure. Replace alloca with dynamic memory
allocations.

Bug: 139945549
Bug: 142475221
Test: mm
Change-Id: I1a154b479c8da66e25d20dced6bf9ae269b906f8
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>