MC-4150: Widget placeholder and variable placeholder styling is broken on inline editing

- Added waits to reduce flakiness

Author: Hwashiang Yu

app/code/Magento/PageBuilder/Test/Mftf/Test/AdminPageBuilderSliderCommonTests.xml

@@ -1582,6 +1582,7 @@
         <executeJS function="return window.getComputedStyle(document.evaluate(&quot;{{SlideOnBackend.variablePlaceholder('1')}}&quot;, document.body).iterateNext()).getPropertyValue('background-color')" stepKey="getVariableStyle" />
         <executeJS function="return window.getComputedStyle(document.evaluate(&quot;{{SlideOnBackend.widgetPlaceholder('1')}}&quot;, document.body).iterateNext()).getPropertyValue('background-color')" stepKey="getWidgetStyle" />
         <click selector="{{SlideOnBackend.tinymce('1')}}" stepKey="focusOnEditorArea2" after="commentValidateStageAfterSave"/>
+        <waitForPageLoad stepKey="waitForTextEditor2" after="focusOnEditorArea2"/>
         <waitForElement selector="{{SlideOnBackend.variablePlaceholder('1')}}" stepKey="waitForVariableElement"/>
         <waitForElement selector="{{SlideOnBackend.widgetPlaceholder('1')}}" stepKey="waitForWidgetElement"/>
         <executeJS function="return window.getComputedStyle(document.evaluate(&quot;{{SlideOnBackend.variablePlaceholder('1')}}&quot;, document.body).iterateNext()).getPropertyValue('background-color')" stepKey="getVariableStyleAfterSave" />

app/code/Magento/PageBuilder/Test/Mftf/Test/AdminPageBuilderTextTest.xml

@@ -2435,6 +2435,7 @@
         <!--Input variable into stage-->
         <comment userInput="Input variable into stage" stepKey="commentInputVariableIntoStage"/>
         <click selector="{{TextOnStage.tinymce('1')}}" stepKey="focusOnEditorArea1"/>
+        <waitForPageLoad stepKey="waitForTextEditor1"/>
         <actionGroup ref="addVariableToTinyMCEInline" stepKey="addVariableToTinyMCE">
             <argument name="variable" value="TinyMCEVariableBaseURL"/>
         </actionGroup>