[jdk13u-dev] RFR: 8216557: Aarch64: Add support for Concurrent Class Unloading

[Sergey Nazarkin]

I'd like to backport feature implemented for x86 platform but missed for aarch64. The patch doesn't not apply cleanly for following files:
1. [8234562](https://bugs.openjdk.java.net/browse/JDK-8234562) was not backported yet, so release_store/load_acquire are part of OrderAccess class
2. [8234737](https://bugs.openjdk.java.net/browse/JDK-8234737) is missed, so Atomic::add use old function signature
3. macroAssembler_aarch64.hpp copyright year
4. sharedRutime.cpp contains [8253375](https://bugs.openjdk.java.net/browse/JDK-8253375) that confuses patcher not expected it

Tested with hotspot tier1/2

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

Commit messages:
 - Fix for missed 8234736 and 8234562
 - Backport 739e8e322d568ab051a905c6369f4b6280f2ee22

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/282/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=282&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8216557
  Stats: 374 lines in 16 files changed: 348 ins; 5 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/282.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/282/head:pull/282

PR: https://git.openjdk.java.net/jdk13u-dev/pull/282