[US] Configure buildpack builder image

[rohanKanojia]

Component

JKube Kit

Task description

Related to #439

As a user using JKube to build the container image of my application leveraging buildpacks, I want to configure buildpack builder image to something else, so that I can override the base image from which the buildpack's build environment is constructed.

Expected Behavior

As a user, I'm able to customize buildpack builder image, so that I can change the way buildpacks are building application's container image.

Acceptance Criteria

Given:

• User wants to build image of his application leveraging buildpacks.
• User wants to use different builder image than default builder image

When:

• User provides builderImage in jkube's image configuration

Then:

• JKube uses the user provided builderImage in the buildpack build

[rohanKanojia]

To tackle this, we first might want to get #2378 in. This adds configuration options of BuildStrategies other than docker inside ImageConfiguration