The initial implementation for this was provided by kaetemi, originally
as a mount flag. However, it has been modified here to be self-contained
in an explicit runtime function that can be called after mount.
The reasons for an explicit function:
1. lfs_mount stays a strictly readonly operation, and avoids pulling in
all of the write machinery.
2. filesystem-wide operations such as lfs_fs_grow can be a bit risky,
and irreversable. The action of growing the filesystem should be very
intentional.
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One concern with this change is that this will be the first function
that changes metadata in the superblock. This might break tools that
expect the first valid superblock entry to contain the most recent
metadata.
Christopher Haster
34b5b39551