Merge patch series "cred: rework {override,revert}_creds()"

Christian Brauner <brauner@kernel.org> says:

For the v6.13 cycle we switched overlayfs to a variant of
override_creds() that doesn't take an extra reference. To this end I
suggested introducing {override,revert}_creds_light() which overlayfs
could use.

This seems to work rather well. This series follow Linus advice and
unifies the separate helpers and simply makes {override,revert}_creds()
do what {override,revert}_creds_light() currently does. Caller's that
really need the extra reference count can take it manually.

* patches from https://lore.kernel.org/r/20241125-work-cred-v2-0-68b9d38bb5b2@kernel.org: (29 commits)
  cred: remove unused get_new_cred()
  nfsd: avoid pointless cred reference count bump
  cachefiles: avoid pointless cred reference count bump
  dns_resolver: avoid pointless cred reference count bump
  trace: avoid pointless cred reference count bump
  cgroup: avoid pointless cred reference count bump
  acct: avoid pointless reference count bump
  io_uring: avoid pointless cred reference count bump
  smb: avoid pointless cred reference count bump
  cifs: avoid pointless cred reference count bump
  cifs: avoid pointless cred reference count bump
  ovl: avoid pointless cred reference count bump
  open: avoid pointless cred reference count bump
  nfsfh: avoid pointless cred reference count bump
  nfs/nfs4recover: avoid pointless cred reference count bump
  nfs/nfs4idmap: avoid pointless reference count bump
  nfs/localio: avoid pointless cred reference count bumps
  coredump: avoid pointless cred reference count bump
  binfmt_misc: avoid pointless cred reference count bump
  aio: avoid pointless cred reference count bump
  ...

Link: https://lore.kernel.org/r/20241125-work-cred-v2-0-68b9d38bb5b2@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>