Description

This PR relaxes the implicit Sized bound on the CanonicalSerialize and CanonicalDeserialize blanket implementations for Rc<T>, Arc<T>, and Cow<'_, T>.

Previously, these implementations required T: Sized, which prevented serialization/deserialization of types like Cow<'a, [U]> even when U implemented the necessary traits. This change adds the ?Sized bound to T in the relevant impl blocks within serialize/src/impls.rs, allowing these types to be used.

closes: #973

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (master)
• Linked to GitHub issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests - Note: Unit tests covering the ?Sized cases (e.g., Cow<'a, [T]>) should be added.
• Updated relevant documentation in the code - Note: No specific documentation updates were required for this change.
• Added a relevant changelog entry to the Pending section in CHANGELOG.md - Note: A changelog entry needs to be added.
• Re-reviewed Files changed in the GitHub PR explorer - Note: Please double-check the changes in serialize/src/impls.rs.