RFR: 8293295: Add type check asserts to java_lang_ref_Reference accessors [v2]

[Coleen Phillimore]

On Fri, 2 Sep 2022 08:21:11 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> From a discussion in [JDK-8293207](https://bugs.openjdk.org/browse/JDK-8293207) / #10117 it was brought up that the Weak/Soft and Phantom specific accessor in java_lang_ref_Reference does not assert that the type is valid.
>
> Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add is_soft and is_weak

Marked as reviewed by coleenp (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/10139