feat(pipelineRef): conditionally load childExecutions when pipelineRef is enabled

[edgarulg]

When pipelineRef is enabled with the following changes: https://github.com/spinnaker/orca/pull/4842 When click on the "View Pipeline Execution" in a execution with PipelineRef trigger Deck is not able to render parentExecution because it does not know how to handle a PipelineRefTrigger.

As part of this changes I defined a new feature flag in deck that conditionally retrieve parent executions when the user visit the SingleExecutionDetails component in the UI.

How to enable Setting.js needs to define the pipelineRefEnabled flag. window.spinnakerSettings.feature.pipelineRefEnabled = true;