Add isTieredSupported method to c.o.j.t.Platforms

Some tests may depend on tested JVM's tiered compilation support.
At the moment the only way to check it is to start a new JVM with +TieredCompilation and check if it's output contain message about "unsupported option" or to run tested JVM with +TieredCompilation and check that TieredCompilation flag is disabled.

These approaches are far from ideal because it either increase test's execution time, or require additional dependencies (like JMX or WhiteBox API).

Fortunately there is a "sun.management.compiler" property that contain compier(s) name and in case when TieredCompilation is supported it contain "Tiered Compilers" substring.

A new method "isTieredSupported" should be added to c.o.j.t.Platforms in order to check tiered compilation availability by looking at "sun.management.compiler" value.