* Support native_type for tables when using the C++ object API.
If native_type is specified on a table:
- No object API struct type is generated.
- The object API refers to the table by its native_type.
- UnPack and Create<TableName> methods are declared but not defined; as they
must be user-provided.
* Add tests for native_type on tables.
* Add documentation for native_type on tables.
Per the definition of --gen-compare: only generate comparators for object API
generated structs. Types annoated with native_type must define their own
comparators if `--gen-compare` is enabled.
Also enables --gen-compare for native_type_test and fixes the test by adding a
comparator for the Native::Vector3D type.
Previously: X::Pack forwarded to CreateX.
Now: CreateX will forward to X::Pack.
This is a step toward enabling using native types for tables when using the
object API. When defining a native table, the user will be able to define a
custom X::Pack method (which is more consistent with the existing native_type
functionality for structs). By reversing the order of the dependencies, CreateX
can continue to be auto-generated and will use the custom X::Pack method when
overriden for native_type tables.
cosmith-nvidia