Fix memory corruption on removal / update of cheats with the same address hash

[max-m]

Previously instead of resizing the GB_cheat_hash_t to fit the new (smaller) number of cheats a new chunk of (uninitialized) memory was used.
Now we shrink the GB_cheat_hash_t by using realloc instead.

I have tested this change by:

1. Applying the following patch:

diff --git a/SDL/main.c b/SDL/main.c
index 5b2164d9..0d2710d9 100644
--- a/SDL/main.c
+++ b/SDL/main.c
@@ -805,6 +805,15 @@ restart:
     }
     else {
         GB_load_rom(&gb, filename);
+
+        GB_add_cheat(&gb, "Cheat #0", 0x0000, 0x00, 0x12, 0x34, false, false);
+        GB_add_cheat(&gb, "Cheat #1", 0x3456, 0x12, 0x78, 0x90, true, true);
+        GB_add_cheat(&gb, "Cheat #2", 0x3456, 0x12, 0x78, 0x90, false, true);
+        GB_add_cheat(&gb, "Cheat #3", 0x3456, 0x12, 0x78, 0x90, true, false);
+        GB_add_cheat(&gb, "Cheat #4", 0x0995, 0xFF, 0xab, 0x42, false, true);
+        GB_add_cheat(&gb, "Cheat #5", 0xcdef, 0xab, 0x00, 0x00, false, true);
+        GB_add_cheat(&gb, "Cheat #6", 0x0000, 0x00, 0x00, 0x00, false, false);
+        GB_add_cheat(&gb, "Cheat #7", 0xffff, 0xff, 0xff, 0xff, true, true);
     }
     
     /* Configure battery */

2. Loading a game
3. Toggling a cheat so the cheat database gets saved to the file system
4. Loading the same game again

Previously step 4 would have crashed:

[New Thread 0x7ffff6442700 (LWP 182590)]

SameBoy v0.15.8ffff57b2700 (LWP 182591)]
[New Thread 0x7fffeddaf700 (LWP 182646)]
[New Thread 0x7fffedd6e700 (LWP 182647)]
> 
Thread 1 "sameboy" received signal SIGSEGV, Segmentation fault.
0x0000555555567ad3 in GB_remove_cheat ()
(gdb) bt
#0  0x0000555555567ad3 in GB_remove_cheat ()
#1  0x0000555555568532 in GB_load_cheats ()
#2  0x00005555555ab394 in run ()
#3  0x00005555555aa66d in main ()