[jdk17u] RFR: 8269897: Shenandoah: Resolve UNKNOWN access strength, where possible

[Aleksey Shipilev]

On Tue, 24 Aug 2021 09:59:01 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Clean backport to fix a serious Shenandoah bug.
> 
> Additional testing:
>  - [x] `jcstress` now passes
>  - [x] `hotspot_gc_shenandoah` passes
>  - [x] `tier1` with `-XX:+UseShenandoahGC` passes
>  - [x] `tier2` with `-XX:+UseShenandoahGC` passes

Got the push approval.

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

PR: https://git.openjdk.java.net/jdk17u/pull/37