Update doc for data_enum props.

Even if all enums are supported, we still want getSupportedValuesList
to return a valid result if implemented.

This CL also adds several missing require_supported_values_list
annotations. This annotation means that if HasSupportedValueInfo
is not null, hasSupportedValuesList must be true.

Test: None
Bug: 383184445
Flag: EXEMPT no code change
Change-Id: I83686e25114114691f6314802ac5c93a1b4daddf