Do not enforce paragraph constraint for copy ctr

Update SpannableStringBuilder, SpannedString and SpannableString classes
so that they don’t enforce paragraph constraint for copy constructors.
If a paragraph constraint is not satisfied for a span, that span is not
copied. Before this change it would throw an exception.

Test: New tests added for SpannableStringBuilder and SpannableString
      cts-tradefed run cts -m CtsTextTestCases
Bug: 36511794

Change-Id: I62abf08a8d4fe7e342ed97b8e8c3a577a9397e39