[Feature Request]: Add manual (non-API based) process to interact with app for end-2-end testing

### Feature description

### Problem

`{shinytest2}` e2e tests are currently created around `AppDriver$set_input` that will make the necessary changes via `javascript: Shiny.setInput` function (within `{chromote}` session).

Current approach successfully tests the app, but it lacks the real interactions that users have with the app, that is:
- Is the input being used visible / existing in the UI
- Can the user interact with it

### Idea
- Add to API functions that find `` elements and can modify value (triggering `observe` callbacks in `R`)
- methods for filter panel interaction to modify filters (alternative to `set_active_filter_selection`)
- methods to change encoding panel (alternative to `set_module_input`)

### Code of Conduct

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### Contribution Guidelines

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### Security Policy

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