Add Unit Tests for Preprocess Function in preprocess.go

[coderabbitai]

This issue tracks the task of ensuring the correctness of the preprocessing logic by adding unit tests for the function and its helper functions, as discussed in the pull request review.

Context:

• Pull Request: feat(x/intent)!: ability for modules to dynamically resolve variables on Action creation #139
• Comment: feat(x/intent)!: ability for modules to dynamically resolve variables on Action creation #139 (comment)

The unit tests should cover various scenarios to validate the functionality of the function and its helper functions within .

[Pitasi]

In general, the status of unit tests for the shield package it's not great, I took some shortcuts to push this thing out.

The code looks fairly well-separated to me, so adding new unit tests (maybe fuzzing as well) should be easy.