OV model hashing: fix the hashing of the weights (#33631)
### Details:
- If my analysis is correct, before this PR, the model hashing function
computes a hash for each constants buffer. The intention was then to
combine these constants hashes in this `OstreamHashWrapperBin::xsputn`.
But there seems to be a bug, `OstreamHashWrapperBin::xsputn` combines
the _length_ of the hashes (which is `sizeof(uint64_t)`) instead of the
hash values. The end result is, models that use the same graph, but
different weights values, will get the same hash from OV.
### Tickets:
- *EISW-198709*
