RFR: 8310311: Serial: move Generation::contribute_scratch to DefNewGeneration [v4]

[Albert Mingkun Yang]

> Simple cleanup to move a method from base-class to  sub-class.
> 
> Test: hotspot_gc

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

  const

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14540/files
  - new: https://git.openjdk.org/jdk/pull/14540/files/04d3a6b0..afdbfeed

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14540&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14540&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14540.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14540/head:pull/14540

PR: https://git.openjdk.org/jdk/pull/14540