RFR: 8253495: CDS generates non-deterministic output

[Ioi Lam]

This patch makes the result of "java -Xshare:dump" deterministic:
- Disabled new Java threads from launching. This is harmless. See comments in jvm.cpp
- Fixed a problem in hashtable ordering in heapShared.cpp
- BasicHashtableEntry has a gap on 64-bit platforms that may contain random bits. Added code to zero it.
- Enabled checking of $JAVA_HOME/lib/server/classes.jsa in make/scripts/compare.sh

Note:  $JAVA_HOME/lib/server/classes_ncoops.jsa is still non-deterministic. This will be fixed in [JDK-8282828](https://bugs.openjdk.java.net/browse/JDK-8282828).

Testing under way:
- tier1~tier5
- Run all *-cmp-baseline jobs 20 times each (linux-aarch64-cmp-baseline, windows-x86-cmp-baseline, .... etc).

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

Commit messages:
 - Merge branch 'master' into 8253495-cds-generateds-non-deterministic-output-2
 - fixed test
 - more fixes
 - 8253495: CDS generates non-deterministic output

Changes: https://git.openjdk.java.net/jdk/pull/7748/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7748&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253495
  Stats: 73 lines in 12 files changed: 49 ins; 7 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7748.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7748/head:pull/7748

PR: https://git.openjdk.java.net/jdk/pull/7748