API change to define account attributes and add

the get and set methods.

Bug: 330326187
Bug: 423022561
Flag: android.provider.new_account_attributes_api_enabled
Test: atest ContactsContract_AccountAttributesTest
API-Coverage-Bug: 423023779

	modified:   core/api/current.txt
	modified:   core/java/android/provider/ContactsContract.java
        modified:   core/java/android/provider/flags.aconfig

Change-Id: I61a938000aa10c85e71549137ac7a6a8f81c9d7f