Use a flag instead of a "Transit Node" for "Dependent tasks that can be ran in parallel"

[Basemm]

Goals

1. Instead of using a fake task "Transit Node", we can use a feature flag like "useDependencyAwareParallelism"

Non-goals

No response

Background

In "Dependent tasks that can be ran in parallel", The user needs to create a transit node "fake task" to be able to run in parallel.
The problem is that

1. Such a transit task is confusing, as a developer can easily forget about this hack, and later on, when he finds no "transit" tasks in package.json he will be tempted to remove the task "Note that this hack is done in a json file where we cannot introduce a comment to clarify".
2. He might use a task name that's not unique enough and will be created in the future, thus becoming a useless dependency

Proposal

Instead of using a fake task "Transit Node", we can use a feature flag like "useDependencyAwareParallelism"