Remove redundancy in conformance definitions in ZAP XMLs

[ethanzhouyc]

In ZAP XML, both formats like optional="true" and <mandatoryConform> are used to define compliance, creating redundancy and confusion:

<attribute side="server" code="0x0004" name="CurrentY" define="COLOR_CONTROL_CURRENT_Y" type="int16u" max="0xFEFF" default="0x607D" reportable="true" optional="true">
      <mandatoryConform>
        <feature name="XY"/>
      </mandatoryConform>
</attribute>

Users don’t know which takes precedence and both must be updated manually. Changing one without updating the other can cause inconsistencies.

Proposed solution:

1. For pure mandatory attributes, no conformance listed at all. optional="false" is disallowed.
2. For pure optional (O) attributes, allow only optional="true" so we can use the shorthand attribute representation in the XML.
3. For anything else, disallow having the optional attribute entirely, list longhand conformance.