RFR: 8286339: compiler/c2/irTests/TestEnumFinalFold.java fails if Enum/String methods are not inlined

[Aleksey Shipilev]

As shown in the bug, the test relies on test methods in `Enum` and `String` to be inlined for constant folding to happen. In some testing modes, this does not happen. The fix is to force inlining for methods that test uses. It is kinda odd to ask force inlining of system class methods, but it does not seem problematic.

Additional testing:
 - [x] Test now passes in unusual test modes reported
 - [x] Test still passes in default test modes on x86_32 and x86_64

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/8625/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8625&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286339
  Stats: 7 lines in 2 files changed: 5 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8625.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8625/head:pull/8625

PR: https://git.openjdk.java.net/jdk/pull/8625