[15] RFR: 8241802: [Graal] compiler/loopopts/TestLogSum.java timed out

[Doug Simon]

Please review this change cherry-picked from upstream Graal to fix a problem where compiling a method with many nested loops took too long.
The heart of the fix (authored by Gilles Duboscq) is to limit the amount of work done by the LoopFullUnrollPhase.

https://bugs.openjdk.java.net/browse/JDK-8241802
https://dougxc.github.io/webrevs/8241802/index.html

Testing: hs-tier1,hs-tier2,hs-tier3-graal

-Doug