Fix duplicated Modal code when loaded using AJAX

[mvorisek]

discovered during investigation of #1732

wrapping demos/data-action/jsactions-panel.php RightPanel demo works well even if wrapped inside Loader

duplicated code/ID is now tested in Behat after every step

  Scenario:                                        # tests-behat/callback.feature:12
    Given I am on "_unit-test/callback-nested.php" # Behat\MinkExtension\Context\MinkContext::visit()
    Then I press button "Load1"                    # Atk4\Ui\Behat\Context::iPressButton()
    Then I should see "Loader-1"                   # Behat\MinkExtension\Context\
                                                     MinkContext::assertPageContainsText()
    Then I press button "Load2"                    # Atk4\Ui\Behat\Context::iPressButton()
    │
    ╳  Exception: Page contains elements with duplicate ID:
         "atk_icon", "_ea0591c61f4b3107cf54838053b3adc3___useraction_modalexecutor",
         "_395f2da8a6a5c80767b0042937355326__tion_modalexecutor_loader",
         "_5fc141f467ea245de8f9515e9dba36b5__modalexecutor_loader_view",
         "_54e1cbc5bc6bbbb943063a6b5646b718__action_modalexecutor_view",
         "_59434c8e5978a6c002cbfdf93e3567b5__modalexecutor_view_button",
         "_365d92f1164005c843c56306fed35810__dalexecutor_view_button_2",
         "_365d92f1164005c843c56306fed35810__dalexecutor_view_button_3",
         "_f0a382c18a3f238d2ca01ecfe1d8bfac__seraction_modalexecutor_2",
         "_10ceb07386588d34599519a11fd9c342__on_modalexecutor_2_loader",
         "_d767499edd1aa3fc1207a1e884d12391__dalexecutor_2_loader_view",
         "_451b4b9ca5c98b9c0e30300079193a29__tion_modalexecutor_2_view",
         "_e35de19f435359fb1223eb830dbe63b5__dalexecutor_2_view_button",
         "_8b700a87c50e78df6714556cb335e1ca__lexecutor_2_view_button_2",
         "_8b700a87c50e78df6714556cb335e1ca__lexecutor_2_view_button_3"
       in src/Behat/Context.php:190
    ╳  Stack trace:
    ╳  #0 src/Behat/Context.php(67): Atk4\Ui\Behat\Context->assertNoInvalidNorDuplicateId()
    │
    └─ @AfterStep # Atk4\Ui\Behat\Context::waitUntilLoadingAndAnimationFinished()