[Eva] Emits a warning when some builtins propagate some garbled mix value.

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

src/plugins/eva/domains/cvalue/builtins_memory.ml

src/plugins/eva/domains/cvalue/cvalue_domain.ml

src/plugins/eva/domains/cvalue/cvalue_transfer.ml

src/plugins/eva/domains/cvalue/cvalue_transfer.mli

tests/builtins/oracle/memcpy.res.oracle

tests/builtins/oracle/memset.res.oracle

tests/builtins/oracle_gauges/memcpy.res.oracle

tests/value/oracle_equality/addition.res.oracle

tests/value/oracle_equality/assigns.res.oracle

tests/value/oracle_octagon/assigns.res.oracle

tests/value/oracle_symblocs/assigns.res.oracle