RFR: 8364588: Export the NPE backtracking functionality to general null-checking APIs [v3]

[Chen Liang]

On Tue, 5 Aug 2025 14:53:03 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> This is intended to be an API directly called by future null-check APIs, like `Objects.requireNonNull` or `Checks.nullCheck`. I initially had code for rNN but decided to withhold that for a future patch since it involves CSR and other evaluations not related to this patch's efforts.
>
> Don't add APIs without uses; it speculative and the API may not be what is really needed.

Should I open a dependent PR to prove that this is exactly what we need to unblock [Objects::requireNonNull message enhancements](https://bugs.openjdk.org/browse/JDK-8233268)?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26600#discussion_r2254627867