RFR: 8331921: Hotspot assembler files should use common logic to setup exported functions

[Magnus Ihse Bursie]

As seen in [JDK-8331541](https://bugs.openjdk.org/browse/JDK-8331541), if we are not consistently setting all assembler directives correctly, we can get errors that are not detected by the linker.

We should stop duplicating this code and create a unified macro to properly setup functions, and use it everywhere.

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

Commit messages:
 - Fix copyright headers
 - Fix building on macos/aarch64
 - Use % instead of @ due to arm assembler
 - 8331921: Hotspot assembler files should use common logic to setup exported functions

Changes: https://git.openjdk.org/jdk/pull/19138/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19138&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331921
  Stats: 604 lines in 22 files changed: 124 ins; 347 del; 133 mod
  Patch: https://git.openjdk.org/jdk/pull/19138.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19138/head:pull/19138

PR: https://git.openjdk.org/jdk/pull/19138