* feat(plugins): allow language packs to declare a native display name
Plugin language packs can set contributes.languagePacks[].displayName so
the Settings language picker shows 中文（繁體） instead of
`zh-TW — pluginKey`. Omitted names keep the previous fallback label.
Fixes#13031
* refactor(plugins): inline language-pack picker label and guard displayName
Inline the one-line picker label fallback, type-check displayName in the
registration guard, drop issue refs from comments, and trim tests.
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Co-authored-by: OrcaWin <293788423+OrcaWin@users.noreply.github.com>
BingZandOrcaWin
64c12b0f89