Text this: “Wenn dunkel mir ist der Sinn,/Den Kunst und Sinnen hat Schmerzen/Gekostet von Anbeginn” (“When Dark Are My Mind and Heart/Which Paid from the Beginning/In Grief for Thought and Art”): Hölderlin in the “Hölderlin Tower”—Contemporary and Modern Diagnoses of His Illness, and Literary (Self-)Therapy