RFR: 8209186: Rename SimpleThresholdPolicy to TieredThresholdPolicy

[Claes Redestad]

Hi,

Nils recently reminded me that we should rename the 
SimpleThresholdPolicy following the merge with AdvancedThresholdPolicy[0].

Webrev: http://cr.openjdk.java.net/~redestad/8209186/open.00/

Bug: https://bugs.openjdk.java.net/browse/JDK-8209186

While this is mostly a straightforward rename, I also took the liberty 
of inlining simpleThresholdPolicy.inline.hpp into 
tieredThresholdPolicy.cpp (it was previously shared between simple- and 
advancedThresholdPolicy.cpp).

Thanks!

/Claes

[0] https://bugs.openjdk.java.net/browse/JDK-8202711