Fixed handful of block_size-related bugs found by CI

- Valgrind-detected memory leak in test_superblocks.

- Valgrind-detected uninitialized lfs->block_size in lfs_init caused by
  an unintended sed replacement.

- Said sed replacement also changed the implementation of the v1 portion
  of lfs_migrate, this is out of scope and caused migrate to fail, which
  fortunately CI noticed.

- We also need to copy the block_size/block_count configs in v1 so that
  low-level bd operations still work.

- le-conversion in test_evil now matters due to difference in
  LFS_ERR_CORRUPT/LFS_ERR_INVAL paths during lfs_mount. This is good
  because we're actually testing for loop detection not pointer
  out-of-bounds as intended.

tests/test_superblocks.toml

@@ -330,6 +330,7 @@ code = '''
             {LFS_MKTAG(LFS_TYPE_SUPERBLOCK, 0, 8), "littlefs"},
             {LFS_MKTAG(LFS_TYPE_INLINESTRUCT, 0, sizeof(superblock)),
                 &superblock})) => 0;
+    lfs_deinit(&lfs) => 0;
 
     // known block_size/block_count
     cfg->block_size = BLOCK_SIZE;
@@ -461,6 +462,7 @@ code = '''
             {LFS_MKTAG(LFS_TYPE_SUPERBLOCK, 0, 8), "littlefs"},
             {LFS_MKTAG(LFS_TYPE_INLINESTRUCT, 0, sizeof(superblock)),
                 &superblock})) => 0;
+    lfs_deinit(&lfs) => 0;
 
     // known block_size/block_count
     cfg->block_size = BLOCK_SIZE;
@@ -521,6 +523,7 @@ code = '''
             {LFS_MKTAG(LFS_TYPE_SUPERBLOCK, 0, 8), "littlefs"},
             {LFS_MKTAG(LFS_TYPE_INLINESTRUCT, 0, sizeof(superblock)),
                 &superblock})) => 0;
+    lfs_deinit(&lfs) => 0;
 
     // known block_size/block_count
     cfg->block_size = BLOCK_SIZE;