refactor: remove deprecated ToInternalValue() (#41020)

* refactor: do not use deprecated ToInternalValue() in ElectronExtensionLoader::FinishExtensionLoad()

Co-authored-by: Charles Kerr <charles@charleskerr.com>

* refactor: do not use deprecated ToInternalValue() in NotificationPresenterWin::SaveIconToFilesystem()

Co-authored-by: Charles Kerr <charles@charleskerr.com>

* chore: rename temp variable to now_usec for clarity

Co-authored-by: Charles Kerr <charles@charleskerr.com>

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Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Charles Kerr <charles@charleskerr.com>