Add kubectl 1.17-based image

Currently we are using kubectl 1.14-based image named as registry.gitlab.com/gitlab-org/gitlab-build-images:gitlab-helm3-kubectl1.14, but kubectl 1.14 was already deprecated, so it is time to upgrade it.

Where the image is used

Initially the image is designed to use one for Review Apps of GitLab Rails app (gitlab-org/gitlab) cf. https://gitlab.com/gitlab-org/gitlab/-/blob/v13.10.0-ee/.gitlab/ci/review.gitlab-ci.yml.

https://sourcegraph.com/search?q=repo:gitlab.com/gitlab-org+gitlab-helm3-kubectl1.14&patternType=literal&case=yes

post note after !387 (merged)

We got 87.7% reduction in size 😍 as follows:

$ docker images registry.gitlab.com/gitlab-org/gitlab-build-images
REPOSITORY                                           TAG                          IMAGE ID            CREATED             SIZE
registry.gitlab.com/gitlab-org/gitlab-build-images   gitlab-helm3.5-kubectl1.17   91f91485d26d        8 hours ago         168MB
registry.gitlab.com/gitlab-org/gitlab-build-images   gitlab-helm3-kubectl1.14     34ff1ce43979        8 weeks ago         1.34GB

cf.

• &5149 (closed)