[Feature request] [UI/UX] Redesign the module selection as a nested list of buttons.

[vedhav]

Currently, we display the module selection buttons inside a dropdown menu with just the labels of the module groups above them, in case of nested modules we concatenate the labels of all parents to showcase the label information. However, a better way to display this would be to showcase the module selection buttons as a nested tree structure that looks something like this for the following two examples:

Example one: modules code

modules <- modules(
  example_module("One"),
  example_module("Two"),
  example_module("Two"),
  teal.modules.general::tm_variable_browser("Variable Browser"),
  modules(
    label = "Nest level 1",
    example_module("Two"),
    example_module("Double Nested module"),
    modules(
      label = "Nest level 2",
      example_module("Inception two"),
      modules(
        label = "Nest level 3",
        example_module("Double Inception")
      )
    )
  ),
  modules(
    label = "Nested",
    example_module("Nested one"),
    example_module("Nested two")
  )
)

Example two: modules code

modules <- modules(
  example_module("Study Information"),
  example_module("Data Table"),
  example_module("Variable Browser"),
  example_module("Demographic Table"),
  modules(
    label = "Disposition",
    example_module("Study Disposition"),
    example_module("Treatment Disposition")
  ),
  modules(
    label = "Exposure",
    example_module("Study Treatment Exposure")
  ),
  modules(
    label = "Adverse Events",
    example_module("AE Overview"),
    example_module("AE by Term"),
    example_module("AE by Term/Grade"),
    example_module("AE by Grade"),
    example_module("Adverse Events by SMQ"),
    example_module("AE Overview Plot"),
    example_module("Common AE Plot"),
    example_module("Butterfly Plot"),
    example_module("AE by Action Taken")
  ),
  modules(
    label = "Patient Profiles",
    example_module("Swimlane Plot"),
    example_module("AE Patient Profiles"),
    example_module("Lab Values")
  ),
  modules(
    label = "Tumor Response",
    example_module("Response Table"),
    example_module("Time to Response"),
    example_module("Clinical Benefit"),
    example_module("Percent Change in SLD (Spider Plot)"),
    example_module("Best Percent Change in SLD (Waterfall Plot)"),
    example_module("Duration of Response (Swimlane Plot)")
  ),
  modules(
    label = "Time To Event",
    example_module("Time To Event Table"),
    example_module("Kaplan Meier Plot")
  ),
  modules(
    label = "Lab Results",
    example_module("Lab Abnormality")
  ),
  modules(
    label = "Concomitant Medications",
    example_module("Concomitant Medications by PT")
  )
)

this span could have a class to change its look. I think it could be more visible

Originally posted by @gogonzo in #1548 (comment)