fix: path for update.xml for loading extensions

[archandatta]

Note

Aligns update.xml URLs with the actual installed extension directory to prevent path mismatches.

• In UploadExtensionsAndRestart, after unzipping, call policy.RewriteUpdateXMLUrls(update.xml, <name>) (non-fatal on error)
• Add RewriteUpdateXMLUrls in policy with extensionPathRegex to replace /extensions/[^/]+/ with /extensions/<name>/

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