Renamed high-level spam tests to include *_spam_*

These are our current set of general-purpose high-level tests that can
be turned to when needing to test a wide range of filesystem operations.

They were getting a bit hard to keep track of without a consistent
prefix, especially since no individual test suite can actually use all
of them at the same time.

Now, finding these tests is as simple as: ./scripts/test.py -L *_spam_*

I also renamed a couple because their names were starting to get
ridiculous. I mean just look at
test_badblocks_alternating_spam_orphanzombiedir_fuzz...

- *_spam_orphanzombie_fuzz    -> *_spam_oz_fuzz
- *_spam_orphanzombiedir_fuzz -> *_spam_ozd_fuzz
- *_spam_file_pl_fuzz         -> *_spam_f_pl_fuzz
- *_spam_filedir_pl_fuzz      -> *_spam_fd_pl_fuzz

Here are all of the current spam tests and contexts we use them in:

                traversal               badblocks   relocations
                |     gc    ck    grow  |     powerloss   exhaustion
  dir_many      y     y           y     y     y     y
  dir_fuzz      y     y     y     y     y           y     y
  file_many     y     y           y     y     y     y
  file_fuzz     y     y     y     y     y           y     y
  fwrite_fuzz   y     y     y           y                 y
  oz_fuzz       y     y     y     y     y           y     y
  ozd_fuzz      y     y     y     y     y           y     y
  f_pl_fuzz                       y           y     y
  fd_pl_fuzz                      y           y     y

tests/test_gc.toml

@@ -2468,7 +2468,7 @@ code = '''
     lfsr_unmount(&lfs) => 0;
 '''
 
-[cases.test_gc_spam_orphanzombie_fuzz]
+[cases.test_gc_spam_oz_fuzz]
 defines.GC_STEPS = [-1, 1, 2, 10, 100, 1000]
 defines.MKCONSISTENT = [false, true]
 defines.LOOKAHEAD = [false, true]
@@ -2824,7 +2824,7 @@ code = '''
     lfsr_unmount(&lfs) => 0;
 '''
 
-[cases.test_gc_spam_orphanzombiedir_fuzz]
+[cases.test_gc_spam_ozd_fuzz]
 defines.GC_STEPS = [-1, 1, 2, 10, 100, 1000]
 defines.MKCONSISTENT = [false, true]
 defines.LOOKAHEAD = [false, true]