fix: do not consider implicit dependencies from action references in dead code branches

[stefreak]

What this PR does / why we need it:
This PR changes getContextLookupReferences to ignore dead code
branches

Which issue(s) this PR fixes:

Fixes an issue where we considered implicit dependencies from action references in dead code branches.

Addititional info:

There was an alternate solution attempt, here: #6849

One of the benefits of the approach of detecting dead branches is that it now also works with logical AND (&&), logical OR (||), ternary expressions (? :) and if block expressions (${if ...}) and not just with structural if operators ($if: yaml keys).

Example / minimal repro:

kind: Project
apiVersion: garden.io/v1
name: test
environments:
 - name: local
variables:
 disabled: ${true}
---
kind: Run
type: exec
name: myrun
spec:
  command: [echo, "${ !var.disabled ? actions.deploy.mydeploy.outputs.logs : '<not executed>'}"]
---
kind: Deploy
type: exec
name: mydeploy
disabled: ${var.disabled}
spec:
  deployCommand: [echo, "${var.disabled ? 'I should not run' : 'I should run'}"]

Command: garden run myrun
Expected behaviour: the deploy "mydeploy" should not be executed.

The docs for the disabled flag do not reflect the current behaviour where we execute disabled actions, if another action references one of their outputs. This is a separate issue that will be dealt with in a separate PR.

[stefreak]

Alternative approach for #6849

[twelvemo]

This is great work and a real fun read! Together with the good test coverage this really looks good to go!

[twelvemo]

This is some smart reasoning!

[stefreak]

Hahah!

[twelvemo]

super nice to cover all these test cases!

[eysi09]

This is great work and a real fun read! Together with the good test coverage this really looks good to go!

Agreed! Was still reading through it but childrenEligibleForRecursion made me smile. And also agree that it's good to go!