Rework the tree_viz example to only read from file

**Description**
 - Slim down the tree viz example so it only reads from file and does
   not generate trees
 - Modify the existing example data so that it has a single delimiter
   with keys and values

**Motivation**
The tree generation part is less useful and I felt like making this
example do only a single thing well was a better use-case.

**Testing Done**
Ran it for a subset of the dictionary file.

examples/example-data/medium_tree.txt

@@ -1,7 +1,7 @@
-1,2,3,4,5,6,A
-2,4,6,8,10,12,B
-1,2,3,4,7,8,C
-1,2,3,4,5,9,D
-2,4,6,8,10,14,E
-2,4,6,8,10,16,F
-2,4,6,8,10,18,G
+123456|A
+24681012|B
+123478|C
+123459|D
+24681014|E
+24681016|F
+24681018|G

examples/example-data/medium_tree_delete_without_merge.txt

@@ -1,6 +1,6 @@
-1,2,3,4,5,6,A
-2,4,6,8,10,12,B
-1,2,3,4,7,8,C
-1,2,3,4,5,9,D
-2,4,6,8,10,14,E
-2,4,6,8,10,18,G
+123456|A
+24681012|B
+123478|C
+123459|D
+24681014|E
+24681018|G

examples/example-data/small_tree_with_prefix.txt

@@ -1,4 +1,4 @@
-1,2,3,4,5,6,A
-2,4,6,8,10,12,B
-1,2,3,4,7,8,C
-1,2,3,4,5,9,D
+123456|A
+24681012|B
+123478|C
+123459|D

examples/example-data/small_tree_with_prefix_delete_fixup_prefix.txt

@@ -1,3 +1,3 @@
-1,2,3,4,5,6,A
-2,4,6,8,10,12,B
-1,2,3,4,5,9,D
+123456|A
+24681012|B
+123459|D

examples/example-data/small_tree_with_prefix_delete_pull_up_root.txt

@@ -1,3 +1,3 @@
-1,2,3,4,5,6,A
-1,2,3,4,7,8,C
-1,2,3,4,5,9,D
+123456|A
+123478|C
+123459|D

examples/example-data/small_tree_with_prefix_delete_pull_up_single_node.txt

@@ -1,3 +1,3 @@
-1,2,3,4,5,6,A
-2,4,6,8,10,12,B
-1,2,3,4,7,8,C
+123456|A
+24681012|B
+123478|C