fix: update wait and set task syntax

[arminhammer]

What this PR does / why we need it:
This PR fixes a couple of inconsistencies between the spec and the sdk that I ran into:

1. The Wait Task has the property wait (https://github.com/serverlessworkflow/specification/blob/main/dsl-reference.md#wait), but in the current code it is set to duration. This PR renames it to wait to align with the spec.

2. The Run Task Script (https://github.com/serverlessworkflow/specification/blob/main/dsl-reference.md#script-process) a. the spec defines a stdin property that is missing in the current code. This PR adds that property.
   b. the spec defines arguments as a list of strings, but the current code has it defined as a HashMap. This PR updates it to a Vec<String> to match the spec.

3. The Set Task (https://github.com/serverlessworkflow/specification/blob/main/dsl-reference.md#set) defines the set property as being either a map or a string type, with the string type being an expression. The current code defines it as a HashMap, making it impossible to define it as a string expression. This PR introduces a complex type SetValue, which can be either a HashMap or an Expression, adding support for either type.

Special notes for reviewers:
I tried to add useful unit tests to test and validate the new behavior.

Additional information (if needed):

[cdavernas]

Looks great to me! Thanks ❤️

Can I however ask you to sign-off your commits so that DCO passes?

[arminhammer]

Sorry, forgot to sign the commit! Should be fixed now and ready to go.