treewide: fix typos in docs and comments

[JohnRTitor]

This PR

• Improves documentation by cleaning up typo and spelling mistakes

Closes https://github.com/koverstreet/bcachefs-tools/pull/129

Adopted from the above PR to remove merge conflict.

[koverstreet]

If you really want to do this you need to drop the changes to libbcachefs/, linux/, include/, and raid/; those are mostly imported from elsewhere.

[JohnRTitor]

@koverstreet Done.