Add cURL support in the alpine image

Description

In order to add the support of interactive web terminal in the Helm Chart project, the cURL library is needed to interact with K8s REST API.

Unfortunately, cURL library is not available by default in the runner alpine image and the wget library available by default doesn't support certificate to make the API calls.

More context is available in the following comments:

• gitlab-org/charts/gitlab-runner!320 (comment 743264361)
• gitlab-org/charts/gitlab-runner!320 (comment 753686425)

Proposal

Add cURL library when build the runner alpine image

Links to related issues and merge requests / references

• Related issue: gitlab-org/charts/gitlab-runner#79 (closed)
• Related MR: gitlab-org/charts/gitlab-runner!320 (merged)