[sh/jdk11] Shenandoah: revert shared JFR changes to match upstream

[Aleksey Shipilev]

Current sh/jdk11 fails to build on arm32:

* For target hotspot_variant-server_libjvm_gtest_objs_BUILD_GTEST_LIBJVM_link:
/home/buildbot/worker/build-shenandoah-jdk11-linux/build/build/linux-arm-normal-server-fastdebug/hotspot/variant-server/libjvm/objs/jfrJniMethod.o:
In function `JfrPeriodicEventSet::requestEvent(JfrEventId)':
/home/buildbot/worker/build-shenandoah-jdk11-linux/build/build/linux-arm-normal-server-fastdebug/hotspot/variant-server/gensrc/jfrfiles/jfrPeriodic.hpp:189:
undefined reference to `JfrPeriodicEventSet::requestShenandoahHeapRegionInformation()'
collect2: error: ld returned 1 exit status
* For target hotspot_variant-server_libjvm_objs_BUILD_LIBJVM_link:
/home/buildbot/worker/build-shenandoah-jdk11-linux/build/build/linux-arm-normal-server-fastdebug/hotspot/variant-server/libjvm/objs/jfrJniMethod.o:
In function `JfrPeriodicEventSet::requestEvent(JfrEventId)':
/home/buildbot/worker/build-shenandoah-jdk11-linux/build/build/linux-arm-normal-server-fastdebug/hotspot/variant-server/gensrc/jfrfiles/jfrPeriodic.hpp:189:
undefined reference to `JfrPeriodicEventSet::requestShenandoahHeapRegionInformation()'
collect2: error: ld returned 1 exit status

I believe this is because we have the leftover hunk in metadata.xml:

https://builds.shipilev.net/patch-openjdk-shenandoah-jdk11/src/hotspot/share/jfr/metadata/metadata.xml.sdiff.html

...which fails to build when Shenandoah is disabled (as it is for arm32). The actual block that is
used by Shenandoah is actually in src/hotspot/share/jfr/metadata/metadata-shenandoah.xml now. The
fix is to revert metadata.xml to the upstream state, basically the reverse of the sdiff above.

Testing: arm32 cross build

-- 
Thanks,
-Aleksey