refactor(tutor): reimplement interactive marks as extmark in Lua

Problem:
From https://matrix.to/#/!cylwlNXSwagQmZSkzs:matrix.org/$Ofj-TFIsEMbp0O9OhE8xuZSNi-nhRLtZTOgs6JRLNrs?via=matrix.org&via=gitter.im&via=mozilla.org

In lesson 2.6, users are asked to remove the second, forth and fifth
lines with `dd` command, then they are asked to undo twice to make the
text go back to original state. But after that, the mark ✗ appears
again, which confuses the user because they think they do something
wrong. This is a limitation with the current implementation, which is
based on line number only.

Solution:
Reimplement interactive marks as extmarks in Lua. This also make the
feature less fragile, as users can remove, add some arbitrary lines
without breaking the interactive marks.

Co-authored-by: Justin M. Keyes <justinkz@gmail.com>

runtime/tutor/en/vim-01-beginner.tutor

@@ -304,7 +304,7 @@ it would be easier to simply type two d's to delete a line.
 
  3. Now move to the fourth line.
 
- 4. Type `2dd`{normal} to delete two lines, then press `u`{normal} twice to undo all three lines.
+ 4. Type `2dd`{normal} to delete two lines.
 
 1)  Roses are red,
 2)  Mud is fun,

runtime/tutor/en/vim-01-beginner.tutor.json

@@ -12,11 +12,11 @@
     "273": -1,
     "292": "This line of words is cleaned up.",
     "309": "1)  Roses are red,",
-    "310": "3)  Violets are blue,",
-    "311": "6)  Sugar is sweet",
-    "312": "7)  And so are you.",
-    "313": "7)  And so are you.",
-    "314": "7)  And so are you.",
+    "310": "",
+    "311": "3)  Violets are blue,",
+    "312": "",
+    "313": "",
+    "314": "6)  Sugar is sweet",
     "315": "7)  And so are you.",
     "335": "Fix the errors on this line and replace them with undo.",
     "381": -1,

runtime/tutor/ja/vim-01-beginner.tutor.json

@@ -11,13 +11,13 @@
     "233": "誰かがこの行の最後を2度タイプしました。",
     "272": -1,
     "291": "この行の単語は綺麗になった。",
-    "308": -1,
-    "309": -1,
-    "310": -1,
-    "311": -1,
-    "312": -1,
-    "313": -1,
-    "314": -1,
+    "308": "1)  薔薇は赤く",
+    "309": "",
+    "310": "3)  菫は青く",
+    "311": "",
+    "312": "",
+    "313": "6)  砂糖は甘く",
+    "314": "7)  そして貴方も",
     "335": "この行の間違いを修正し、後でそれらの修正を取り消します。",
     "381": -1,
     "382": -1,

runtime/tutor/zh/vim-01-beginner.tutor

@@ -287,7 +287,7 @@ This ABC DE line FGHI JK LMN OP of words is Q RS TUV cleaned up.
 
  3. 现在移动到第 4 行。
 
- 4. 输入 `2dd`{normal} 来删除两行，然后按两次 `u`{normal} 来恢复这三行。
+ 4. 输入 `2dd`{normal} 来删除两行。
 
 1)  Roses are red,
 2)  Mud is fun,

runtime/tutor/zh/vim-01-beginner.tutor.json

@@ -14,11 +14,11 @@
     "259": -1,
     "276": "This line of words is cleaned up.",
     "292": "1)  Roses are red,",
-    "293": "3)  Violets are blue,",
-    "294": "6)  Sugar is sweet",
-    "295": "7)  And so are you.",
-    "296": "7)  And so are you.",
-    "297": "7)  And so are you.",
+    "293": "",
+    "294": "3)  Violets are blue,",
+    "295": "",
+    "296": "",
+    "297": "6)  Sugar is sweet",
     "298": "7)  And so are you.",
     "318": "Fix the errors on this line and replace them with undo.",
     "319": "Fix the errors on this line and replace them with undo.",