[messagepack-rs] Deserialization functions pass uninitialized memory to user-provided Read

Affected versions of this crate passed an uninitialized buffer to a
user-provided Read instance in:

• deserialize_binary
• deserialize_string
• deserialize_extension_others
• deserialize_string_primitive

This can result in safe Read implementations reading from the uninitialized
buffer leading to undefined behavior.

References

• https://github.com/otake84/messagepack-rs/issues/2
• https://rustsec.org/advisories/RUSTSEC-2021-0092.html
• https://github.com/advisories/GHSA-m325-rxjv-pwph