Remove Quiz results block from core

Setup (before patch)

The following steps should be run on a Moodle site without the patch.

1. Login as admin.
2. Create two courses C1 and C2.
3. Add a quiz to each course.
4. Go to Site administration / Plugins / Blocks / Manage blocks
5. Go to Quiz results (disabled) and enabled clicking on the eye icon to show the block.
6. Go to course C1 and Turn editing on.
7. Go to the quiz and Add a block and add these blocks:
   1. Quiz results (disabled)
   2. Activity results
8. Go to Configuring a Quiz results (disabled) block and set the weight to 5.
9. Go to course C2 and Turn editing on.
10. Go to the quiz and Add a Quiz results (disabled) block.
11. Go to Configuring a Quiz results (disabled) block and set the weight to 6. 
12. Check the following SQL query return 2 rows. Annotate the ids

    SELECT * FROM `mdl_block_instances` WHERE blockname = 'quiz_results'

13. Check the following SQL query return 2 rows(you'll need to replace the ids that you've annotated previously)

    SELECT * FROM `mdl_block_positions` WHERE blockinstanceid in (ID1,ID2)

TEST (after patch)

1. Apply the patch and run the upgrade process.
2. Verify it ends without error.
3. Login as admin.
4. Go to "Site administration > Plugins > Plugins overview".
5. Verify there is no longer a mention of 'Quiz results' (block_quiz_results).
6. Go to courses C1 and C2 and turn editing on.
7. Go to the quizzes and confirm you don't see   Quiz results (disabled) block
8. Go to Site administration / Plugins / Blocks / Manage blocks
9. Verify there is no longer a mention of 'Quiz results' (block_quiz_results).
10. Check the following SQL query is empty:

    SELECT * FROM `mdl_block_instances` WHERE blockname = 'quiz_results'

11. Check the following SQL is empty (you'll need to replace the ids that you've annotated previously in the setup)

    SELECT * FROM `mdl_block_positions` WHERE blockinstanceid in (ID1,ID2)