RFR: 8345647: Fix recent NULL usage backsliding in Shenandoah

[Kim Barrett]

On Tue, 10 Dec 2024 09:28:00 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Well, it is not technically a `NULL -> nullptr` changes we handle with PRs like these, but I guess it is good to have a consistent wording.

We've also been changing "NULL" in comments and strings.  This avoids having an identifier in those that isn't actually
present in code.  Perhaps more importantly, it prepares for JDK-8343802.  In comments and strings we sometimes use
"null" and sometimes use "nullptr", depending on whether the context code-like or not.

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PR Comment: https://git.openjdk.org/jdk/pull/22647#issuecomment-2536242322