Follow swift test naming convention; add test method docstring

Author: kastiglione

lldb/test/API/functionalities/breakpoint/swift_property_accessors/TestPropertyAccessorBreakpoints.py renamed to lldb/test/API/functionalities/breakpoint/swift_property_accessors/TestSwiftPropertyAccessorBreakpoints.py

@@ -6,6 +6,7 @@
 class TestCase(TestBase):
     @swiftTest
     def test(self):
+        """Test that a breakpoint on a property accessor can be set by name."""
         self.build()
         exe = self.getBuildArtifact("a.out")
         target = self.dbg.CreateTarget(exe)