QDoc: Group property role notes in outputHEADdev

When a signal (or other role) applies to multiple properties, QDoc
repeats the same “<Role> for property X.” line for each property.
This creates noisy, hard-to-scan documentation.

This change modifies `Generator::generateAddendum()` such that it groups
properties by `FunctionRole`. This allows QDoc to emit a single
admonition per role, listing all applicable properties. For example:

    Notifier signal for properties Foo, Bar, and Baz.

Properties are listed alphabetically; roles follow enum order (Getter,
Setter, Resetter, Notifier, Bindable). This ensures deterministic output.
There's no change to semantics or links, as this is a wording/format
improvement only.

The change also includes a validate-output test (HTML/DocBook/WebXML)
that demonstrates the previous repetition and the new grouped output.

Fixes: QTBUG-86490
Pick-to: 6.10 6.9 6.8
Change-Id: I5221c25f8040cc617dd2ec595f58c95d16120ac7
Reviewed-by: Topi Reiniö <[email protected]>

0 files changed, 0 insertions, 0 deletions