[Eva] add typing checks for malloc builtins; fix some tests

src/plugins/value/domains/cvalue/builtins.ml

src/plugins/value/domains/cvalue/builtins_malloc.ml

tests/builtins/malloc-deps.c

tests/builtins/malloc-optimistic.c

tests/builtins/malloc.c

tests/builtins/malloc_memexec.c

tests/builtins/memexec-malloc.c

tests/builtins/oracle/malloc-deps.res.oracle

tests/builtins/oracle/memexec-malloc.res.oracle