[lworld] RFR: 8378767: [lworld] Rename Makefile functions and variables related to preview mode

[David Beaumont]

On Thu, 26 Feb 2026 14:57:32 GMT, David Beaumont <duke at openjdk.org> wrote:

> Renames value class related functions and variables in Makefiles to reflect the more general use for preview mode classes/resources (where appropriate).
> 
> As preview mode is enabled in mainline builds, it will no longer be limited to value classes and their semantics.
> 
> After this change, the work "value" appears only once in the modified files (outside of comments) when defining GENERATED_PREVIEW_SUBDIRS.
> 
> This does change the `_the.$(MODULE).valueclasses` target to be `_the.$(MODULE).preview` but that should not be an issue.

make/CompileJavaModules.gmk line 140:

> 138: PREVIEW_CLASSES_LABEL := preview
> 139: # Module relative path in which preview classes/resources are placed.
> 140: PREVIEW_PATH := META-INF/preview

New constant to avoid repeating this path fragment.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/2175#discussion_r2859519531