RFR: 8259870: zBarrier.inline.hpp should not include javaClasses.hpp

[Ioi Lam]

zBarrier.inline.hpp is a popular header file (it's included by about 430 out of ~1000 hotspot .o files). It includes javaClasses.hpp only for the inline function verify_on_weak(), which is used only for assert purposes in debug builds.

javaClasses.hpp is large and in turn pulls in other large header files. If we move verify_on_weak() into zBarrier.cpp and stop including javaClasses.hpp in zBarrier.inline.hpp, building hotspot is about 0.5% faster. The number of .o files that include javaClasses.hpp is reduced from 459 to 175.

Testing: 
Tested with mach5: tier1, builds-tier2, builds-tier3, builds-tier4 and builds-tier5. Also locally: aarch64, arm, ppc64, s390, x86, and zero.

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Commit messages:
 - 8259870: zBarrier.inline.hpp should not include javaClasses.hpp

Changes: https://git.openjdk.java.net/jdk/pull/2120/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2120&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259870
  Stats: 33 lines in 3 files changed: 17 ins; 13 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2120.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2120/head:pull/2120

PR: https://git.openjdk.java.net/jdk/pull/2120