Fix email auto link when there are two chars in local part

Fix email auto link when there are two chars in local part

Email auto linking used to accept either a single char or more than 2
chars in the local part. Updated the regular expression to accept 1 or
more chars.

Test: added test to cts.LinkifyTest
Test: bit -t CtsTextTestCases:android.text.util.cts.LinkifyTest
Test: bit -t FrameworksCoreTests:android.util.PatternsTest
Test: bit -t FrameworksCoreTests:android.text.util.LinkifyTest
Test: bit -t CtsWidgetTestCases:android.widget.cts.TextViewTest

Bug: 64467661
Change-Id: I4e28a344ff1bc50da353b9490eaaec99a751bffb