Add getSelection and getSelectionPath tests

Adds basic tests that cover the functionality of getSelection and
getSelectionPath. These tests illustrate why, when having a multiline
selection over two lines, four rectangles are generated instead of the
expected two.

Test: bit FrameworksCoreTests:android.text.LayoutTest
Test: bit FrameworksCoreTests:android.text.LayoutTest#testGetSelectionWithEmptySelection
Test: bit FrameworksCoreTests:android.text.LayoutTest#testGetSelectionWithASingleLineSelection
Test: bit FrameworksCoreTests:android.text.LayoutTest#testGetSelectionWithMultilineSelection_secondLineSelectionEndsBeforeFirstCharacter
Test: bit FrameworksCoreTests:android.text.LayoutTest#testGetSelectionWithMultilineSelection_secondLineSelectionEndsAfterACharacter
Test: bit FrameworksCoreTests:android.text.LayoutTest#testGetSelectionPathWithASingleLineSelection
Change-Id: Idc13794c12e5b76dc221c45df99af337457a2fef