RFR: 8344263: GenShen: Reduce extraneous log messages at INFO level [v5]

[Aleksey Shipilev]

On Mon, 18 Nov 2024 21:56:01 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Genshen logs a lot of fine level detail at `gc=info`. This category should be reserved for major phase changes in the gc cycle.
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update test, remove unused header, use proper case for old gen phases

I looked at `-Xlog:gc` with this patch, and it looks good. I say we do this.

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Marked as reviewed by shade (Committer).

PR Review: https://git.openjdk.org/shenandoah/pull/540#pullrequestreview-2446093205