RFR: Fix ShenandoahFullGC worker stats handling

[Aleksey Shipilev]

Current Windows builds fail like this:


c:\buildbot\worker\build-shenandoah-jdkx-windows\build\src\hotspot\share\gc\shenandoah\shenandoahFullGC.cpp(1074): error C2131: expression did not evaluate to a constant
c:\buildbot\worker\build-shenandoah-jdkx-windows\build\src\hotspot\share\gc\shenandoah\shenandoahFullGC.cpp(1074): note: failure was caused by a read of a variable outside its lifetime
c:\buildbot\worker\build-shenandoah-jdkx-windows\build\src\hotspot\share\gc\shenandoah\shenandoahFullGC.cpp(1074): note: see usage of 'num_workers'
c:\buildbot\worker\build-shenandoah-jdkx-windows\build\src\hotspot\share\gc\shenandoah\shenandoahFullGC.cpp(1075): error C2131: expression did not evaluate to a constant
c:\buildbot\worker\build-shenandoah-jdkx-windows\build\src\hotspot\share\gc\shenandoah\shenandoahFullGC.cpp(1075): note: failure was caused by a read of a variable outside its lifetime
c:\buildbot\worker\build-shenandoah-jdkx-windows\build\src\hotspot\share\gc\shenandoah\shenandoahFullGC.cpp(1075): note: see usage of 'num_workers'
make[3]: *** [lib/CompileJvm.gmk:143: /cygdrive/c/buildbot/worker/build-shenandoah-jdkx-windows/build/build/windows-x86_64-server-fastdebug/hotspot/variant-server/libjvm/objs/shenandoahFullGC.obj] Error 1


Instead of doing auto-alloc with worker count that is unknown at compile time, use resource area for allocations.

Additional testing:
 - [x] Linux x86_64 `hotspot_gc_shenandoah`
 - [x] Windows x86_64 build

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

Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/shenandoah/pull/62/files
 Webrev: https://webrevs.openjdk.java.net/?repo=shenandoah&pr=62&range=00
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/shenandoah/pull/62.diff
  Fetch: git fetch https://git.openjdk.java.net/shenandoah pull/62/head:pull/62

PR: https://git.openjdk.java.net/shenandoah/pull/62