Improve print for teal_data_module/teal_transform_module to be more useful

[vedhav]

Currently, the teal_data_module and teal_transform_module just prints the UI and Server functions and the attributes when we print them. It will be nice if we can format this to showcase key information.

Similar to #1378. Additionally, it will be helpful if we can use this format to further show more information in the print method of the teal_module that uses transformations.

Example object and current print:

tdm <- teal_data_module(
  ui = function(id) {
    ns <- NS(id)
    actionButton(ns("submit"), label = "Load data")
  },
  server = function(id) {
    moduleServer(id, function(input, output, session) {
      eventReactive(input$submit, {
        data <- within(
          teal_data(),
          {
            dataset1 <- iris
            dataset2 <- mtcars
          }
        )
        datanames(data) <- c("dataset1", "dataset2")

        data
      })
    })
  }
)

> tdm
$ui
function(id) {
    ns <- NS(id)
    actionButton(ns("submit"), label = "Load data")
  }

$server
function(id) {
        data_out <- server(id)
        decorate_err_msg(
          assert_reactive(data_out),
          pre = sprintf("From: 'teal_data_module()':\nA 'teal_data_module' with \"%s\" label:", label),
          post = "Please make sure that this module returns a 'reactive` object containing 'teal_data' class of object." # nolint: line_length_linter.
        )
      }
<environment: 0x000001b695b02828>

attr(,"label")
[1] "data module"
attr(,"class")
[1] "teal_data_module"
attr(,"once")
[1] TRUE