fix(manager): correct OnBeforeManagerPageInit / OnManagerPageInit order

[Ibochkarev]

What does it do?

• Fires manager page init events from modManagerController::render() via invokeManagerPageInitEvents(): OnBeforeManagerPageInit first, then OnManagerPageInit.
• Removes the early OnManagerPageInit invocation from modManagerRequest::handleRequest() (it ran before OnBeforeManagerPageInit in render()).
• Passes OnManagerPageInit a payload of controller config merged with the current request action and namespace (request values win when set).
• Adds PHPUnit coverage for event order and merge behavior (ManagerPageInitEventsTest).

Backward-compatibility note: OnManagerPageInit now runs when the controller renders, not at the beginning of handleRequest(). Code paths that redirect or exit before render() may no longer trigger these two events; listeners that must run earlier should use another system event (e.g. OnHandleRequest).

Why is it needed?

Fixes the incorrect ordering described in the issue: OnBeforeManagerPageInit must run before OnManagerPageInit so plugins can prepare state before the main init event.

How to test

• Run: phpunit -c _build/test/phpunit.xml --filter ManagerPageInitEventsTest
• Manually: open the MODX manager and exercise pages that rely on plugins hooked to OnBeforeManagerPageInit / OnManagerPageInit; confirm expected order and that action / namespace in the event payload match the request.

Related issue(s)/PR(s)

Resolves #9461