feat: Update slugs to use new format

Author: libmartinito

course-definition.yml

@@ -69,7 +69,7 @@ marketing:
 
 stages:
   - legacy_slug: "init"
-    slug: "init"
+    slug: "dr6"
     name: "Print page size"
     difficulty: very_easy
     description_md: |-
@@ -122,7 +122,7 @@ stages:
       do this by parsing a file that uses the [SQLite database file format](https://www.sqlite.org/fileformat.html).
 
   - legacy_slug: "table_count"
-    slug: "table_count"
+    slug: "ce0"
     name: "Print number of tables"
     difficulty: hard
     description_md: |-
@@ -167,7 +167,7 @@ stages:
       [SQLite database file format](https://www.sqlite.org/fileformat.html).
 
   - legacy_slug: "table_names"
-    slug: "table_names"
+    slug: "sz4"
     name: "Print table names"
     difficulty: hard
     description_md: |-
@@ -200,7 +200,7 @@ stages:
       the count of tables like in the previous stage, you'll print out the names of tables too.
 
   - legacy_slug: "row_counts"
-    slug: "row_counts"
+    slug: "nd9"
     name: "Count rows in a table"
     difficulty: medium
     description_md: |-
@@ -239,7 +239,7 @@ stages:
       `SELECT COUNT(*) FROM <table>`.
 
   - legacy_slug: "read_single_column"
-    slug: "read_single_column"
+    slug: "az9"
     name: "Read data from a single column"
     difficulty: hard
     description_md: |-
@@ -290,7 +290,7 @@ stages:
       `SELECT <column> FROM <table>`.
 
   - legacy_slug: "read_multiple_columns"
-    slug: "read_multiple_columns"
+    slug: "vc9"
     name: "Read data from multiple columns"
     difficulty: hard
     description_md: |-
@@ -322,7 +322,7 @@ stages:
       In this stage, your sqlite3 implementation will need to execute a SQL statement of this form: `SELECT <column1>,<column2> FROM <table>`.
 
   - legacy_slug: "where"
-    slug: "where"
+    slug: "rf3"
     name: "Filter data with a WHERE clause"
     difficulty: hard
     description_md: |-
@@ -351,7 +351,7 @@ stages:
       an index, so you'll visit all records in a table and then filter out the matching ones.
 
   - legacy_slug: "table_scan"
-    slug: "table_scan"
+    slug: "ws9"
     name: "Retrieve data using a full-table scan"
     difficulty: hard
     description_md: |-
@@ -394,7 +394,7 @@ stages:
       an index, so you'll visit all records in a table and then filter out the matching ones.
 
   - legacy_slug: "index_scan"
-    slug: "index_scan"
+    slug: "nz8"
     name: "Retrieve data using an index"
     difficulty: hard
     description_md: |-