[lworld] RFR: 8371357: [lworld] Remove EnableValhalla

[Coleen Phillimore]

On Tue, 25 Nov 2025 13:37:46 GMT, Paul Hübner <phubner at openjdk.org> wrote:

> Hi all,
> 
> This removes the `EnableValhalla` in favour of the `--enable-preview` flag. Concretely:
> * I've replaced most of the `EnableValhalla` checks with `Arguments::is_valhalla_enabled()`. 
> * Some checks were redundant and could be removed entirely.
> * I've made the `EnableValhalla` flag obsolete.
> * Some tests had to be updated.
> 
> This greatly changes the semantics of tests. I've refined some test groups to make it easier.
> 
> Testing: tiers 1-4.

This seems fine to me with or without a one line include file for is_valhalla_enabled() to test Arguments::enable_preview() or any other change for future preview or valhalla related features.  I think we can fix that for the specific situations when it happens.

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Marked as reviewed by coleenp (Committer).

PR Review: https://git.openjdk.org/valhalla/pull/1759#pullrequestreview-3578330317