RFR: Update copyright lines

[Aleksey Shipilev]

This updates copyright lines on all files Generational Shenandoah touches related to upstream.

Generally, every change should come with actual copyright line. It is agreed in upstream to upgrade the Oracle copyright years, and that is usually required for every incoming PR.

I used a simple ruleset:
  - If the change is small and there is Oracle header, the date is updated to 2023;
  - If the change is small and there only Red Hat header (which we cannot touch), Amazon header is added;
  - If the change is large, Amazon header is added and Oracle header is updated to 2023;

It reverts some of the changes related to upstream, if they do not fit the ruleset above.
Also, existing Amazon headers are updated to new, consistent form.

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

Commit messages:
 - Update copyrights

Changes: https://git.openjdk.org/shenandoah/pull/247/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=247&range=00
  Stats: 228 lines in 193 files changed: 176 ins; 5 del; 47 mod
  Patch: https://git.openjdk.org/shenandoah/pull/247.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/247/head:pull/247

PR: https://git.openjdk.org/shenandoah/pull/247