[CWS] Introduce scope_field for process scope

[Gui774ume]

What does this PR do?

This PR introduces scope_field for scoped variable in set actions.

Motivation

The goal of this field is to provide which field should be used to query the scope of the variable modified in this action. The goal of this field is to allow updating the value of a variable for a different process than the one that triggered the rule.

Example use case: setting the execution context of the target process of a cgroup_write event.

- id: cgroup_write_execution_context
  expression: cgroup_write.pid > 0
  actions:
    - set:
        name: correlation_key
        expression: '"first_${builtins.uuid4}"'
        scope: process
        scope_field: cgroup_write.pid
        inherited: true

Describe how you validated your changes

Tests were added.

Possible Drawbacks / Trade-offs

Additional Notes