Revise the javadoc of requiredSplitTypes and splitTypes

    <!-- List of split types required by this APK to be present in order to function properly,

         separated by commas. The platform will reject installation of an app that is missing

         any required split types. Each split type is an arbitrary string that has no specific

         meaning to the platform, and is only used for matching <code>splitTypes</code> and

         <code>requiredSplitTypes</code>. As an example, if a split requires strings, drawables,

         and native code this value could be "language,density,abi". Default value is null to

         indicate no split types are required. -->

         any required split types. Each split type is a string, and is only used for matching

         <code>requiredSplitTypes</code> and <code>splitTypes</code>. As an example, if this

         APK requires localized string resources, screen density resources, and native code

         this value could be "language,density,abi". Default value is null to indicate no split

         types are required. -->

    <attr name="requiredSplitTypes" format="string" />

    <!-- List of split types offered by this APK, separated by commas. Each split type is an

         arbitrary string that has no specific meaning to the platform, and is only used for

         matching <code>splitTypes</code> and <code>requiredSplitTypes</code>. As an example,

         if a split offers strings and drawables the value could be "language,density". Default

         value is null to indicate no split types are offered. -->

    <!-- List of split types offered by this APK, separated by commas. Each split type is a

         string, and is only used for matching <code>requiredSplitTypes</code> and

         <code>splitTypes</code>. As an example, if this split offers localized string resources,

         and screen density resources the value could be "language,density". Default value is

         null to indicate no split types are offered. -->

    <attr name="splitTypes" format="string" />

    <!-- Flag to specify if this app wants to run the dex within its APK but not extracted or