ddms: Add support for sampling profiler

This CL adds supports for sampling based profiling.

When method profiling is initiated, we detect whether sampling
profiling is supported and if so, we show a dialog that allows
users to select the type of profiling to be performed.

The methods to obtain and display trace data is unchanged.

Change-Id: I8ec1a2c2311d6ffa7f73b5690d71e9d2253d09f2

• ddms/app/src/main/java/com/android/ddms/UIThread.java[diff]
• ddms/ddmuilib/src/main/java/com/android/ddmuilib/DevicePanel.java[diff]
• ddms/ddmuilib/src/main/java/com/android/ddmuilib/vmtrace/VmTraceOptionsDialog.java[Added - diff]