Feature/support prior return value in when clause

[yippie]

Adds the ability to reference output of tasks to determine if subsequent tasks should be run or not.

This pull request enhances the flow runner to support dynamic substitution of prior step return values within a step's when clause, allowing for more flexible and data-driven conditional execution of steps. It also introduces comprehensive tests to validate this new behavior.

Enhancements to flow runner conditional logic:

• Added support for referencing prior step return values in a step's when clause using the ^^path.key syntax. The flow runner now parses and substitutes these references with the actual return values from previous steps before evaluating the condition. [1] [2] [3]

Testing and validation:

• Introduced a new task class _TaskReturnsBoolStr in the test suite to facilitate testing of return value substitution.
• Registered the new return_bool test task in the test project configuration.
• Added multiple tests to verify the new substitution logic, including:
  • Step runs or is skipped based on the substituted value.
  • Multiple substitutions in a single when clause.
  • Proper error handling when a referenced prior step does not exist.

[salesforce-cla]

Thanks for the contribution! It looks like @davidmreed is an internal user so signing the CLA is not required. However, we need to confirm this.