feat: import kubectl get command

[gianarb]

What

This commit replaces the datumctl get command that currently supports
organizations only with the kubectl get command.

DATUMCTL_EXPERIMENTAL=true go run main.go get projects --organization-id personal-org-f9a87347
NAME                   READY   AGE
shippingbytes-jh601e   True    87d

DATUMCTL_EXPERIMENTAL=true go run main.go get domains --project-id shippingbytes-jh601e
NAME       DOMAIN NAME   AGE   VERIFIED
hello-it   hello.it      46h   False

DATUMCTL_EXPERIMENTAL=true go run main.go get organizationmemberships --all-namespaces
NAME                   READY   AGE
shippingbytes-jh601e   True    87d

It also adds support for -v the same used by the kubectl and for two
new commands: api-resources and api-versions

Why

We want to offer a fimilar environment to interact with for users coming from
Kubernetes. No better way to achive that than using the kubectl code itself.

For Reviewer

I decied to open this PR now becuase I am working at it from a couple of days
and the features are there, I want other people to look at it.

The implementation is pretty rusty I am still not sure about how to properly
combine clientcmd.ConfigFlags an the Factory. I wrote Datum implementation to
see if I was able to get somewhere but I feel we can do better. Primarly
because I had to modify the clientcmd to support --all-namespaces and it
sounds pretty wrong!

I am open for suggesitions

[scotwells]

@gianarb FYI I had to run go mod tidy to get this to build on a fresh checkout.

$ go build -o datumctl .
go: updates to go.mod needed; to update it:
        go mod tidy
$ go mod tidy
$ go build -o datumctl .
$ ./datumctl --help
A CLI for interacting with the Datum platform
...