refactor(share/shwap): shwap types improvements

[Wondertan]

Changes here are extracted out of #3421

Notable changes:

• Renamings
  • DataID -> RowNamespaceDataID for consistency with the spec
• Validation method consistency
  • Singe validation method per type
  • Validate, not Verify
• Values over pointers
  • The types are small and copy-friendly, so we can benefit from simplicity and efficiency of using values
• Rearrange method/functions
• Constructors first, then serialization methods, then other methods
• Abstracts away small integers in ID types
  • We use uint16 integers over the wire, which are slightly cumbersome to convert. Here we use int everywhere and convert to uint16 during serialization instead.
• RowsWIthNamespace as an alternative to FilterByNamespace