This should also fix an init error if a -walletdir with a trailing slash
is used on windows. This appears to be a real error and regression
introduced with #20744.
On windows (or at least wine), fs calls that actuallly access the
filesystem like fs::equivalent or fs::exists seem to treat directory
paths with trailing slashes as not existing, so it's necessary to
normalize these paths before using them. This change passes canonical
paths to fs calls validating the -walletdir path to fix this.
d216bc8d76