feat: Support function extract_scalar_key_values

[b41sh]

This PR introduces several enhancements to the RawJsonb type and the Serializer.
Key Changes:

1. RawJsonb::extract_scalar_key_values: Added a new function, extract_scalar_key_values, to the RawJsonb type. This function allows for the extraction of paths and corresponding scalar values from within nested JSON structures. This is particularly useful for querying and manipulating deeply nested data.

2. RawJsonb::to_value: Introduced a new function, to_value, to the RawJsonb type. This function converts a binary JSONB representation into a Value type suitable for in-memory operations. This facilitates easier manipulation and access of JSONB data within the application.

3. Serializer Enhancements: The Serializer now supports a comprehensive set of serialization methods, including:

   • serialize_i128
   • serialize_u128
   • serialize_newtype_struct
   • serialize_newtype_variant
   • serialize_tuple_struct
   • serialize_tuple_variant
   • serialize_struct
   • serialize_struct_variant

   With these additions, all ser::Serializer trait functions are now fully implemented, providing a complete and convenient serialization solution for various data structures.