Improve go modules fulfillment

[Adirio]

• Kubebuilder uses semantic versioning
• Kubebuilder has a v2 or higher
• Kubebuilder versions are listed on pkg.go.dev

Description

Although kubebuilder follows semantic versioning as required by go modules, only versions with major version 0 or 1 are actually obtainable by version with go modules. This can be seen in the link provided above.

The solution is to use a non-existent version and use the timestamp and commit hash to refer to a specific version. For example, operator SDK uses sigs.k8s.io/kubebuilder v1.0.9-0.20201021204649-36124ae2e027 which refers to 36124ae.

In order to solve this, go.mod file needs to be changed to include /v2 at the package name (module sigs.k8s.io/kubebuilder/v2) and internal imports need to reference to this same package.

I think it should definetely be implemented for future versions. However, I'm not sure what should be done with previous v2 versions. As previous versions are released, they are tagged and have their code compressed (it would change imports).

/kind feature

[Adirio]

/cc @droot @mengqiy @DirectXMan12 @camilamacedo86 @estroz

[camilamacedo86]

I think it is totally fine we leave the previous versions as it is. See that kb has not been provided as lib before the plugins be offered.

[pwittrock]

FYI -- for some reason this breaks pkger

[camilamacedo86]

The v2 branch was updated with that already.See: #1878
Then, for the next patch release, it will be done.