[language] automatically call text when they appear directly as a statement; remove autocalling of every text returned by a statement

The previous behavior, where any Text value returned by a line in a Block would be automatically called, may lead to unexpected Text event being written as it is not obvious which line can return a Text value after evaluation.

The new behavior only triggers if a Text node directly appear in the original script as a statement.

test/tests/autocall text statement.ans

@@ -0,0 +1,7 @@
+| Hello
+
+| Wor | + | ld |
+
+(| Hello)!
+
+(| Wor | + | ld |)!