[8u] RFR (S) 8231949: [PPC64, s390]: Make async profiling more reliable

[Aleksey Shipilev]

Original bug:
   https://bugs.openjdk.java.net/browse/JDK-8231949
   https://hg.openjdk.java.net/jdk/jdk/rev/c6cbcc673cd3

We suspect this causes some of the real-world failures on 8u ppc64le, but there is no clear 
reproducer to see if it actually helps. So, this is somewhat of a blind backport.

The 8u patch follows the same footsteps Martin did for 11u backport:
   https://mail.openjdk.java.net/pipermail/jdk-updates-dev/2019-November/002137.html

Namely, we are using the old style for these checks:

-      if (!Method::is_valid_method(m)) return false;
-      if (!Metaspace::contains(m->constMethod())) return false;
+      if (m == NULL || !m->is_valid_method()) return false;
+      if (!Metaspace::contains((const void*)m->constMethod())) return false;

(I would suggest backporting JDK-8207779 that would introduce Method::is_valid_method in 8u, then we 
would rewrite this line back to upstream state).

There are also no s390x parts, because that port is not available in 8u.

8u webrev:
   https://cr.openjdk.java.net/~shade/8231949/webrev.8u.01/

Testing: Linux ppc64le jdk_jfr (no new failures, no new passes)

-- 
Thanks,
-Aleksey