Relocate `Generation.java` to mirror the structure in hotspot. Also, specialize the logic to two concrete generations.
Test: tier1-3 ------------- Commit messages: - sa-move-generation Changes: https://git.openjdk.org/jdk/pull/17844/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17844&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8325860 Stats: 135 lines in 10 files changed: 28 ins; 54 del; 53 mod Patch: https://git.openjdk.org/jdk/pull/17844.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/17844/head:pull/17844 PR: https://git.openjdk.org/jdk/pull/17844
