RFR: 8366065: ZGC: Differentiate Young Collection type strings in statistics

[Axel Boldt-Christmas]

On Thu, 28 Aug 2025 12:21:46 GMT, Joel Sikström <jsikstro at openjdk.org> wrote:

> Hello,
> 
> Currently, two different Young Collection (YC) types print identical strings in the GC statistics at the end of `-Xlog:gc*`. This makes it difficult to distinguish statistics for specific YC types when analyzing logs for performance issues. This PR updates the strings to match the `ZYoungType` enum names, improving traceability and making logs clearer.
> 
> Relevant enum for reference:
> ```c++
> enum class ZYoungType {
>   minor,
>   major_full_preclean,
>   major_full_roots,
>   major_partial_roots,
>   none
> };
> 
> 
> Testing:
> * GHA

Very nice to be able to differentiate the stats logging for the major and minor GC.

We have some mixed terminology already with regards to `prelcean` and `promote all`. 

I think this change is fine and brings the logging in line with the terms used for `ZYoungType`.

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Marked as reviewed by aboldtch (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26986#pullrequestreview-3194985172