tests/sys/fs/fusefs: include iomanip header

[ngie]

Summary

io.cc relies on std::setw(..), which is exported by the iomanip C++
header. Newer versions of GoogleTest don't export this header, so add
the explicit include.

This unbreaks the build with GoogleTest 1.15.2.

Test Plan

With GoogleTest 1.15.2...

$ sudo kyua test -k /usr/tests/sys/fs/fusefs/Kyuafile 
access:main  ->  passed  [0.004s]
allow_other:main  ->  passed  [0.004s]
bad_server:main  ->  passed  [0.004s]
bmap:main  ->  passed  [0.004s]
cache:main  ->  passed  [0.004s]
copy_file_range:main  ->  passed  [0.004s]
create:main  ->  passed  [0.005s]
default_permissions:main  ->  passed  [0.008s]
default_permissions_privileged:main  ->  passed  [0.004s]
destroy:main  ->  passed  [0.004s]
dev_fuse_poll:main  ->  passed  [0.005s]
fallocate:main  ->  passed  [0.005s]
fifo:main  ->  passed  [0.003s]
flush:main  ->  passed  [0.004s]
forget:main  ->  passed  [0.004s]
fsync:main  ->  passed  [0.004s]
fsyncdir:main  ->  passed  [0.004s]
getattr:main  ->  passed  [0.004s]
interrupt:main  ->  passed  [0.005s]
io:main  ->  passed  [0.019s]
last_local_modify:main  ->  passed  [0.004s]
link:main  ->  passed  [0.004s]
locks:main  ->  passed  [0.004s]
lookup:main  ->  passed  [0.004s]
lseek:main  ->  passed  [0.004s]
mkdir:main  ->  passed  [0.005s]
mknod:main  ->  passed  [0.004s]
mount:main  ->  passed  [0.004s]
nfs:main  ->  passed  [0.004s]
notify:main  ->  passed  [0.004s]
open:main  ->  passed  [0.004s]
opendir:main  ->  passed  [0.004s]
read:main  ->  passed  [0.006s]
readdir:main  ->  passed  [0.005s]
readlink:main  ->  passed  [0.004s]
release:main  ->  passed  [0.004s]
releasedir:main  ->  passed  [0.004s]
rename:main  ->  passed  [0.004s]
rmdir:main  ->  passed  [0.004s]
setattr:main  ->  passed  [0.005s]
statfs:main  ->  passed  [0.004s]
symlink:main  ->  passed  [0.005s]
unlink:main  ->  passed  [0.004s]
write:main  ->  passed  [0.006s]
xattr:main  ->  passed  [0.005s]

Results file id is usr_tests_sys_fs_fusefs.20241019-161053-827197
Results saved to /root/.kyua/store/results.usr_tests_sys_fs_fusefs.20241019-161053-827197.db

45/45 passed (0 broken, 0 failed, 0 skipped)

[asomers]

The change LGTM. But the tests ran suspiciously fast. Are you sure that fusefs.ko is loaded?