Update Vignette due to datanames updates

[donyunardi]

Summary

Related to #333, let's update our vignette to fully explain this new feature.

Acceptance Criteria

The following topics must be covered:

• The use of a dot prefix in object names within a teal_data object
• What happens if you don't use a dot prefix
• Behavior when a function is included in teal_data
• How module(datanames) relates to names(teal_data)
• What happens when using module(datanames = "all") vs module(datanames = "<specific data object>")
• What happens when using transform(datanames = "all") vs transform(datanames = "<specific data object>")
• Discussion on set_datanames
• Listing all possible scenarios between module(datanames) and transform(datanames)
  Can use this table as an example: datanames slot in teal_transform_module (ignore @datanames) teal#1334 (comment)

[vedhav]

The information about the dot prefix is already mentioned in the teal.data vignette's hidden objects section.
The information about the modules and datanames should live in the teal package. There is already a vignette about teal_data properties which should be extended with the names sub-section.

I propose that we include the names subsection at the bottom over there and mention about how the names are managed with something that starts like this:

names

The names property stores the character vector listing objects of a teal_data object which are of interest to teal modules.
By default, all the objects in the teal_data environment that do not start with a . are considered of interest.

td <- teal_data() |>
  within({
    iris <- iris
    .hidden_iris <- iris
    cars <- mtcars
  })
names(td)
# [1] "cars" "iris"

Finally, I'll point out that the active discussion and modification around the set_datanames is blocking this issue for now. It would be best if we can conclude those discussions and proceed with this one.