RFR: 8259070: Add jcmd option to dump CDS [v8]

[Yumin Qi]

> Hi, Please review
> 
>   Added jcmd option for dumping CDS archive during application runtime. Before this change, user has to dump shared archive in two steps: first run application with
>   `java -XX:DumpLoadedClassList=<classlist> .... `  
>  to collect shareable class names and saved in file `<classlist>` , then 
>   `java -Xshare:dump -XX:SharedClassListFile=<classlist> -XX:SharedArchiveFile=<archivefile> ...`
>   With this change, user can use jcmd to dump CDS without going through above steps. Also user can choose a moment during the app runtime  to dump an archive.
>    The bug is associated with the CSR: https://bugs.openjdk.java.net/browse/JDK-8259798 which has been approved.
>    New added jcmd option:
>    `jcmd <pid or AppName> VM.cds static_dump <filename>`
>    or
>     `jcmd <pid or AppName> VM.cds dynamic_dump <filename>`
>   To dump dynamic archive, requires start app with newly added flag `-XX:+RecordDynamicDumpInfo`, with this flag, some information related to dynamic dump like loader constraints will be recorded. Note the dumping process changed some object memory locations so for dumping dynamic archive, can only done once for a running app. For static dump, user can dump multiple times against same process. 
>    The file name is optional, if the file name is not supplied, the file name will take format of `java_pid<number>_static.jsa` or `java_pid<number>_dynamic.jsa` for static and dynamic respectively. The `<number>` is the application process ID.
> 
>   Tests: tier1,tier2,tier3,tier4
> 
> Thanks
> Yumin

Yumin Qi has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:

 - Fix revert unintentionally comment, merge master.
 - Merge branch 'master' of ssh://github.com/yminqi/jdk into jdk-8259070
 - Remove CDS.getVMArguments, changed to use VM.getRuntimeVMArguments. Removed unused function from ClassLoader. Improved InstanceKlass::is_shareable() and related test. Added more test scenarios.
 - Remove redundant check for if a class is shareable
 - Fix according to review comment and add more tests
 - Fix filter more flags to exclude in static dump, add more test cases
 - Merge branch 'master' into jdk-8259070
 - Fix white space in CDS.java
 - Add function CDS.dumpSharedArchive in java to dump shared archive
 - 8259070: Add jcmd option to dump CDS

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Changes: https://git.openjdk.java.net/jdk/pull/2737/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2737&range=07
  Stats: 830 lines in 21 files changed: 758 ins; 58 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2737.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2737/head:pull/2737

PR: https://git.openjdk.java.net/jdk/pull/2737