RFR: 8324636: Serial: Remove Generation::block_is_obj [v2]

[Albert Mingkun Yang]

> Trivial moving a method from `Generation` to subclass.

Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:

  review

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17555/files
  - new: https://git.openjdk.org/jdk/pull/17555/files/4f655ef8..8eb6ea6b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17555&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17555&range=00-01

  Stats: 4 lines in 2 files changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/17555.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17555/head:pull/17555

PR: https://git.openjdk.org/jdk/pull/17555