Create helpers to ensure platform api is always provided to acceptance tests

[natalieparellano]

Description

As we're moving toward table tests for acceptance, it's important to always pass the CNB_PLATFORM_API, like here: https://github.com/buildpacks/lifecycle/blob/8d93e588101b22f1e8d3badb9274ebb4bf0894bc/acceptance/analyzer_test.go#L110. We should make it really easy not to forget to pass this variable, maybe with something like h.WithPlatform(platformAPI).

We might consider adding a non-sensical value to the test image, so that the lifecycle would fail if we forget to override it for a specific test.