Align image name and image tags

Definition:

• function: BUILD_TARGET
• custom: BUILD_TAG
• env: ENV
• time: BUILD_DATE

In !209 (merged), image name only consist of function, and custom or time. while the MR is trying to add custom and env in image tags metadata.

• image name: function, and custom or time
• image tags: function and env

If we use the tags to select images, we are missing some criteria.

NOTE: This issue originated from this discussion - #265 (comment 92993), Follow this for more details