allow to customise report-failure-as-issue without the need to modify the GH_AW_FAILURE_REPORT_AS_ISSUE in the lock file manually

[v1v]

If we use reusable GitHub workflows with Agentic Workflows, we cannot easily configure the env variable GH_AW_FAILURE_REPORT_AS_ISSUE when using report-failure-as-issue:

  # Format 1: When false, disables creating failure tracking issues when workflows
  # fail. When true, all failures trigger issues. Defaults to true.
  report-failure-as-issue: true

The alternative consists on modifying the lock files after running the gh aw compile command, see elastic/ai-github-actions#1397

We use reusable github workflows to help with opinionated reusable workflows, where we simplify the usage without the need to recompile the AW.

I'd like to get some configurable way to avoid setting the env variable in the lock file as post-compile step.

[pelikhan]

@copilot make this field a templatable Boolean and allow defining in shared agentic workflows