RFR: 8260408: Shenandoah: adjust inline hints after JDK-8255019

[Aleksey Shipilev]

I was following up on performance testing results for some ongoing work, and realized that there are `ShenandoahMarkContext::mark_strong` calls from `mark_work_loop`. Those callees were supposed to be inlined. I believe it is a simple omission after JDK-8255019 moved `mark_work_loop` code to `shenandoahMark.cpp`.

On a typical workload:

# Before
[44.500s][info][gc,stats] Concurrent Marking  =    0.395 s (a =    11278 us) 
   (n =    35) (lvls, us =     6426,     9473,    11133,    12891,    16476)

# After
[44.405s][info][gc,stats] Concurrent Marking  =    0.337 s (a =     9636 us) 
   (n =    35) (lvls, us =     3770,     7383,     9785,    11328,    16776)

Additional testing:
 - [x] Eyeballing GC hot paths
 - [x] Ad-hoc performance tests

-------------

Commit messages:
 - 8260408: Shenandoah: adjust inline hints after JDK-8255019

Changes: https://git.openjdk.java.net/jdk/pull/2235/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2235&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260408
  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2235.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2235/head:pull/2235

PR: https://git.openjdk.java.net/jdk/pull/2235