RFR: JDK-8260571: Add PrintMetaspaceStatistics to print metaspace statistics upon VM exit [v2]

[Thomas Stuefe]

> This patch adds a new diagnostic boolean switch `PrintMetaspaceStatistics`. When set, it will cause the VM to print a brief report about metaspace occupancy when exiting. It follows the same logic as `PrintNMTStatistics` and similar switches.

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  Rename switch

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2283/files
  - new: https://git.openjdk.java.net/jdk/pull/2283/files/99590267..9e573541

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2283&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2283&range=00-01

  Stats: 3 lines in 2 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2283.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2283/head:pull/2283

PR: https://git.openjdk.java.net/jdk/pull/2283