Plugin does not discover top-level methods in .kt files #847

Description

If we have a file with top-level functions (some Utils.kt), there will be no available methods for testing found (actually, you can't even call an action).

To Reproduce

Steps to reproduce the behavior:

1. Run an empty project in IntelliJ Idea
2. Create a kotlin file with top-level function
3. Try to use the plugin to generate tests

Expected behavior

Opened UTBot dialog

Actual behavior

Nothing happens

Visual proofs (screenshots, logs, images)

Environment

There is no specific environment.

Additional context

There is no additional context.