[5.3] Replace xml_set_object with proper callable parameters

[HLeithner]

Pull Request for Issue # .

Summary of Changes

Replace xml_set_object call by calling set_xml_*_handler with callable object.

Testing Instructions

Test extension installation
Test joomla update

Actual result BEFORE applying this Pull Request

Works (php 8.4 with deprecation warinings)

Expected result AFTER applying this Pull Request

Works (php 8.4 without deprecation warnings)

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[richard67]

It sems that the system tests need to be adapted to this PR, or there is something wrong because they are currently failing: https://ci.joomla.org/joomla/joomla-cms/80456/1/22

Running:  administrator/components/com_joomlaupdate/Update.cy.js                       (19 of 129)

  Test the update retrieval logic
    1) "after each" hook for "Can fetch available updates with valid metadata"

  0 passing (2s)
  1 failing

  1) Test the update retrieval logic
       "after each" hook for "Can fetch available updates with valid metadata":
     Error: Unwanted PHP Warning: "  xml_parse(): Unable to call handler Joomla\\CMS\\Updater\\Adapter\\ExtensionAdapter::startElement() in <b>/tests/www/cmysql/libraries/src/Updater/Adapter/ExtensionAdapter.php</b> on line <b>286</b>"

Because this error occurred during a `after each` hook we are skipping all of the remaining tests.
  at supportCommands/ (webpack://joomla/./node_modules/joomla-cypress/src/support.js:110:0)
...

[HLeithner]

Copy paste issue...