libsysprof-gtk: add new SysprofTimeSeries

This is to replace what is in libsysprof-analyze currently, so we can do
charting in a more flexible manner.

src/libsysprof-gtk/sysprof-time-series-item-private.h

@@ -0,0 +1,33 @@
+/* sysprof-time-series-item-private.h
+ *
+ * Copyright 2023 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+#include "sysprof-time-series-item.h"
+
+G_BEGIN_DECLS
+
+SysprofTimeSeriesItem *_sysprof_time_series_item_new (GObject       *item,
+                                                      GtkExpression *x_expression,
+                                                      GtkExpression *y_expression);
+
+G_END_DECLS