RFR: 8309403: Serial: Remove the useless adaptive size policy in GenCollectedHeap [v4]

[Guoxiong Li]

> Hi all,
> 
> This patch removes the useless code related to the `AdaptiveSizePolicy` in `GenCollectedHeap`.
> As a result, the `SoftRefGenPolicy` is unnecessary too, use `SoftRefPolicy` instead.
> 
> Thanks for the review.
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Treat INCLUDE_G1GC and INCLUDE_SERIALGC as variables.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14296/files
  - new: https://git.openjdk.org/jdk/pull/14296/files/6d233e90..beaa29ff

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14296&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14296&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14296.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14296/head:pull/14296

PR: https://git.openjdk.org/jdk/pull/14296