RFR: JDK-8300087: Replace NULL with nullptr in share/cds/

[Johan Sjölen]

Do the conversion in the share/cds/ sub-directory and all of its files.

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Commit messages:
 - Manual fixes
 -  Replace NULL with nullptr in share/cds/

Changes: https://git.openjdk.org/jdk/pull/12090/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12090&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300087
  Stats: 518 lines in 31 files changed: 0 ins; 0 del; 518 mod
  Patch: https://git.openjdk.org/jdk/pull/12090.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12090/head:pull/12090

PR: https://git.openjdk.org/jdk/pull/12090