Automatic merge from submit-queue (batch tested with PRs 44364, 44361, 42498)
Move v1 helpers
The first 3 commits are other PRs.
This PR move pkg/api/v1/helpers.go to a subpackage, which is almost symmetric to #44296, where pkg/api/helpers.go was moved.
This PR is mostly mechanic, except that
1. moved the 3 methods of Taint and Toleration to pkg/api/methods.go
2. moved constants and types defined in v1/helpers.go to pkg/api/v1/annotataion_key_constants.go and nonstandard_types.go
3. updated staging/copy.sh to copy pkg/api/helpers to client-go, it's otherwise removed from client-go because no other code in client-go depends on the package. Some test code in pkg/controller imports client-go/pkg/api/helpers. After moving api types to its own repo, we can remove these copies of utility function from client-go and ask users to use the ones in the main repo.
(This PR breaks a cyclic import problem i met when I tried to move global variables pkg/api/Scheme and Registry to a subpackage)
e4b5181026