RFR: 8308596: Revert the "keepAlive" workaround from CDS tests

[Calvin Cheung]

This fix reverts the [changeset](https://github.com/openjdk/jdk/commit/0dbe4c5d516a5e43934cb18f3becaf2a7f90999f#diff-4184777f000a8c9284612862ed6169b85030d15fe5ee54c9694e0649613f9d8c) for [JDK-8278131](https://bugs.openjdk.org/browse/JDK-8278131) which was a workaround for the more aggressive sweeping of the code cache issue in an early implementation of loom. The workaround is no longer necessary.

Testing:

- locally on linux-x64 with a promoted loom build
- tiers 1,2,4

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

Commit messages:
 - Revert "8278131: runtime/cds/appcds/dynamicArchive/* tests failing in loom repo"

Changes: https://git.openjdk.org/jdk/pull/14249/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308596
  Stats: 66 lines in 9 files changed: 0 ins; 52 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/14249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14249/head:pull/14249

PR: https://git.openjdk.org/jdk/pull/14249