[Bug]: The filter panel feature does not work well when data/vars have special characters

### What happened?

The namespace creation function for the data and column names can be more robust. Right now the special characters are stripped from the name space which might not be ideal.

```r
library(teal)

app <- init(
within(teal_data(), {
iris <- iris
iris[["Species!"]] <- iris$Species
iris[["Species!@#$%^&*_-+={[()]}:;,<>./?"]] <- iris$Species
}),
modules(
example_module("Module 1"),
example_module("Module 2"),
modules(
label = "Nested modules",
example_module("Module 3"),
example_module("Module 4"),
modules(
label = "Sub nested modules",
example_module("Module 5"),
example_module("Module 6")
)
)
),
filter = teal_slices(
teal_slice(dataname = "iris", varname = "Species", multiple = FALSE),
teal_slice(dataname = "iris", varname = "Species!", multiple = TRUE),
teal_slice(dataname = "iris", varname = "Species!@#$%^&*_-+={[()]}:;,<>./?", multiple = TRUE),
teal_slice(dataname = "iris", varname = "Sepal.Length", multiple = TRUE)
)
)

shinyApp(app$ui, app$server)
```

### sessionInfo()

_No response_

### Relevant log output

_No response_

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