Change multiday fullDay Event behaviour (#3396)

Hey!

This PR should change the behaviour of starting fullDay events that last
several days. The goal was to change the behavior of the "Starting
today, ends T" (T=Tomorrow) event, so it should show how many days it
will occur from the first day on

Before situation:

a fullDay event that started 'today' and ends several days later showed
Today on the first day. The rest of the days it showed X days left.


![grafik](https://github.com/MagicMirrorOrg/MagicMirror/assets/6515818/da4e06cf-3122-44d9-b78a-88f9970c57d4)

Y => Yesterday
T => Tomorrow


Target situation with this commit:
a fullDay event that started 'today' shows 'X days left' from the first
day on and 'Today' on the last day.


![grafik](https://github.com/MagicMirrorOrg/MagicMirror/assets/6515818/c42b9a27-35cf-47b7-9a8f-937a6009f904)

---------

Co-authored-by: Veeck <github@veeck.de>

tests/configs/modules/calendar/long-fullday-event.js

@@ -0,0 +1,28 @@
+/* MagicMirror² Test config for fullday calendar entries over multiple days
+ *
+ * By Paranoid93 https://github.com/Paranoid93/
+ * MIT Licensed.
+ */
+let config = {
+	timeFormat: 12,
+
+	modules: [
+		{
+			module: "calendar",
+			position: "bottom_bar",
+			config: {
+				calendars: [
+					{
+						maximumNumberOfDays: 2,
+						url: "http://localhost:8080/tests/mocks/calendar_test_multi_day_starting_today.ics"
+					}
+				]
+			}
+		}
+	]
+};
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}

tests/configs/modules/calendar/single-fullday-event.js

@@ -0,0 +1,28 @@
+/* MagicMirror² Test config for fullday calendar entries over multiple days
+ *
+ * By Paranoid93 https://github.com/Paranoid93/
+ * MIT Licensed.
+ */
+let config = {
+	timeFormat: 12,
+
+	modules: [
+		{
+			module: "calendar",
+			position: "bottom_bar",
+			config: {
+				calendars: [
+					{
+						maximumNumberOfDays: 2,
+						url: "http://localhost:8080/tests/mocks/calendar_test_full_day_events.ics"
+					}
+				]
+			}
+		}
+	]
+};
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}