Address issues related to testing with shinytest2 the examples (#915)

# Pull Request

Attempts to fix
insightsengineering/coredev-tasks#536 on this
package.

1. system.file don't raise an error (but I need to check if it is empty
or it reports useful info).
2. When there is an error on a shiny session the test of the example
fails.
3. Stop using `load_all` inside test-examples.
4. Checks all examples due to upstream issues being fixed since last
year.


For testing 2 create a new file and add a new file and document to add
this example:

```
#' Example failing
#' @export
#' @examples
#' app <- init(
#' data = teal_data(
#'   new_iris = transform(iris, id = seq_len(nrow(iris))),
#'   new_mtcars = transform(mtcars, id = seq_len(nrow(mtcars)))
#' ),
#' modules = modules(
#'   module(
#'     "Iris Sepal.Length histogram",
#'     server = function(input, output, session, data) {
#'       stop("yada") # 🔍 this will fail the app
#'     },
#'     ui = function(id, ...) {
#'       ns <- NS(id)
#'       plotOutput(ns("hist"))
#'     },
#'     datanames = "new_iris"
#'   )
#' )
#' )
#' if (interactive()) {
#'   shinyApp(app$ui, app$server)
#' }
module_error <- function() {}
```

Then for all check with `R CMD check` or `devtools::test(filter =
"examples")` from plain R session.

Author: llrs-roche

tests/testthat/test-examples.R

@@ -36,10 +36,6 @@ with_mocked_app_bindings <- function(code) {
   # workaround of https://github.com/rstudio/shinytest2/issues/381
   # change to `print(shiny__shinyApp(...))` and remove allow warning once fixed
   mocked_shinyApp <- function(ui, server, ...) { # nolint object_linter.
-    functionBody(server) <- bquote({
-      .hint_to_load_package <- add_facet_labels # Hint to shinytest2 when looking for packages in globals
-      .(functionBody(server))
-    })
     mocked_runApp(do.call(shiny__shinyApp, append(x = list(ui = ui, server = server), list(...))))
   }
 
@@ -135,13 +131,6 @@ with_mocked_app_bindings <- function(code) {
   )
 }
 
-strict_exceptions <- c(
-  # https://github.com/r-lib/gtable/pull/94
-  "tm_outliers.Rd",
-  "tm_g_response.Rd",
-  "tm_a_pca.Rd"
-)
-
 discard_validation_regex <- list(
   "tm_file_viewer.Rd" = "Please select a file\\.",
   "tm_g_distribution.Rd" = "Please select a test"
@@ -155,11 +144,6 @@ for (i in rd_files()) {
       testthat::skip("chromium")
       skip_if_too_deep(5)
       testthat::skip_if_not_installed("pkgload")
-      if (basename(i) %in% strict_exceptions) {
-        op <- options()
-        withr::local_options(opts_partial_match_old)
-        withr::defer(options(op))
-      }
       # Allow for specific validation errors for individual examples
       withr::local_options(
         list(