AK: Make ByteBuffer::try_* functions return ErrorOr<void>

Same as Vector, ByteBuffer now also signals allocation failure by
returning an ENOMEM Error instead of a bool, allowing us to use the
TRY() and MUST() patterns.

AK/StringBuilder.h

@@ -64,7 +64,7 @@ public:
     }
 
 private:
-    bool will_append(size_t);
+    ErrorOr<void> will_append(size_t);
     u8* data() { return m_buffer.data(); }
     u8 const* data() const { return m_buffer.data(); }