RFR: 8365814: Consolidate has_been_archived() and has_been_buffered() in ArchiveBuilder

[Ioi Lam]

On Wed, 20 Aug 2025 04:53:20 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Merged the two methods into one: `ArchiveBuilder::has_been_archived()`. Added comments and asserts to explain what the expected result is.
>
> Good.

Thanks @vnkozlov and @coleenp for the review

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PR Comment: https://git.openjdk.org/jdk/pull/26853#issuecomment-3215578101