EnvTest setup docs need to be updated

[camilamacedo86]

What do you want to happen?

The ENV TEST was changed. So, we need to update the docs to clarifies that as add the new instructions.
See: https://github.com/kubernetes-sigs/controller-runtime/tree/master/tools/setup-envtest#where-does-it-put-all-those-binaries

Then, would be very nice instead of removing the current instructions make it clear when it loses its supports.

Also, note that we probably have related steps in the migration guide from v2 to v3 which seems that needs to be revisited.

Extra Labels

/kind documentation

[camilamacedo86]

c/c @varshaprasad96

[jmrodri]

/cc @varshaprasad96

[varshaprasad96]

/assign @varshaprasad96