[bug] `skip` doesn't work with variables from previous steps

[berlic]

Hey. Thanks for the useful testing tool.

There is and issue that only global variables or variables from other test cases work with 'skip', but not from previous steps within a test case.

Reproducible with this example:

vars:
  static_var: 1
testcases:
- name: skip-works1
  steps:
  - name: do-step
    type: exec
    script: echo .
    vars:
      dynamic_var:
        from: result.code
        default: ""
  - name: dont-skip-step
    type: exec
    script: echo .
    skip:
      - static_var ShouldEqual 1
  - name: skip-step
    type: exec
    script: echo .
    skip:
      - static_var ShouldEqual 0
- name: skip-works2
  steps:
  - name: do-step
    type: exec
    script: echo .
  - name: dont-skip-step
    type: exec
    script: echo .
    skip:
      - skip-works1.dynamic_var ShouldEqual 0
  - name: skip-step
    type: exec
    script: echo .
    skip:
      - skip-works1.dynamic_var ShouldEqual 1
- name: skip-doesnt-work
  steps:
  - name: do-step
    type: exec
    script: echo .
    vars:
      another_dynamic_var:
        from: result.code
        default: ""
  - name: dont-skip-step
    type: exec
    script: echo another_dynamic_var={{.skip-doesnt-work.another_dynamic_var}}
    skip:
      - skip-doesnt-work.another_dynamic_var ShouldEqual 0
  - name: skip-step
    type: exec
    script: echo another_dynamic_var={{.skip-doesnt-work.another_dynamic_var}}
    skip:
      - skip-doesnt-work.another_dynamic_var ShouldEqual 1

I found some abandoned PRs on this matter: #685, but the latest release is sill plagued with this issue.