refactor(shell)!: remove deprecated open API (#3604)

* refactor(shell)!: remove deprecated open API

`open` has been deprecated since 2.1.0 in favor of tauri-plugin-opener.
This removes:

- the `open` command and its `allow-open`/`deny-open` permissions
  (`shell:default` now grants nothing)
- the `plugins > shell > open` configuration; `init()` returns
  `TauriPlugin<R>` again
- `Shell::open`, the `tauri_plugin_shell::open` module and
  `Error::UnknownProgramName`
- the `open` JavaScript function
- the Android and iOS plugins, since `open` was their only command

* chore(examples): drop the now empty shell:default permission set

---------

Co-authored-by: Lucas Nogueira <lucas@crabnebula.dev>

plugins/shell/src/error.rs

@@ -8,15 +8,10 @@ use serde::{Serialize, Serializer};
 
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
-    #[cfg(mobile)]
-    #[error(transparent)]
-    PluginInvoke(#[from] tauri::plugin::mobile::PluginInvokeError),
     #[error(transparent)]
     Io(#[from] std::io::Error),
     #[error("current executable path has no parent")]
     CurrentExeHasNoParent,
-    #[error("unknown program {0}")]
-    UnknownProgramName(String),
     #[error(transparent)]
     Scope(#[from] crate::scope::Error),
     /// Sidecar not allowed by the configuration.