RFR: 8244669: convert clhsdb "mem" command from javascript to java

[Chris Plummer]

clhsdb lost support for the "mem" command when javascript support was removed from SA. This PR is re-adding it by implementing it in Java. The description of the CR contains all the details.

Regarding the clhsdb.html changes for the "examine" command, they are just correctly specifying the existing syntax. No change was actually made to the syntax.

The changes made to the "examine" command are part of a consolidation effort to better share code between "examine" and "mem". "examine" has no functional changes.

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Commit messages:
 - Add support for clhsdb 'mem' command.

Changes: https://git.openjdk.java.net/jdk/pull/6902/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6902&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8244669
  Stats: 158 lines in 3 files changed: 121 ins; 29 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6902.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6902/head:pull/6902

PR: https://git.openjdk.java.net/jdk/pull/6902