RFR: 8261600: NMT: Relax memory order for updating MemoryCounter and fix racy updating of peak values

[Zhengyu Gu]

Currently, MemoryCounter is updated with default memory_order_conservative, it is too strong for updating a counter.

Also, updating peak values with regular assignment, which is racy and broken.

- [x] hotspot_nmt on Linux x86_64 and aarch64

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Commit messages:
 - Update Copyrights
 - init

Changes: https://git.openjdk.java.net/jdk/pull/2527/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2527&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261600
  Stats: 55 lines in 2 files changed: 36 ins; 2 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2527.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2527/head:pull/2527

PR: https://git.openjdk.java.net/jdk/pull/2527