[RFC #0096] Analyzer should write new run image metadata to analyzed.toml

[buildpack-bot]

Spec PR: buildpacks/spec#335

The following fields are added to analyzed.toml:

[run-image]
  [target]
  id = "<target identifer>"               # from io.buildpacks.id label (optional)
  os = "<OS name>"                             # from image config
  arch = "<architecture>"                      # from image config
  variant = "<architecture variant>"           # from image config (optional)
  [target.distribution]
  name = "<OS distribution name>"              # from io.buildpacks.distribution.name label (optional)
  version = "<OS distribution version>"        # from io.buildpacks.distribution.version label (optional)

The analyzer, for newer platform API (0.12 or greater) should read this information from the run image and write it to analyzed.toml.

If target data is missing but the image contains the label io.buildpacks.stack.id with value io.buildpacks.stacks.bionic, the lifecycle SHALL assume the following values:
- run-image.target.os = "linux"
- run-image.target.arch = "x86_64"
- run-image.target.distribution.name = "ubuntu"
- run-image.target.distribution.version = "18.04"