Add PickerLauncher wrapper for media/file pickers. (#361)

* Add `PickerLauncher` wrapper for media/file pickers.

* Add FileProvider path, handle Camera picker and add NoOp implementation to fix tests.

* Move media pickers to their own module.

* Add missing media pickers

* Add feature flag and some extra tests

libraries/textcomposer/src/main/kotlin/io/element/android/libraries/textcomposer/TextComposer.kt

@@ -50,6 +50,7 @@ fun TextComposer(
     onFullscreenToggle: () -> Unit = {},
     onCloseSpecialMode: () -> Unit = {},
     onComposerTextChange: (CharSequence) -> Unit = {},
+    onAddAttachment:() -> Unit = {},
 ) {
     if (LocalInspectionMode.current) {
         FakeComposer(modifier)
@@ -78,6 +79,7 @@ fun TextComposer(
                         }
 
                         override fun onAddAttachment() {
+                            onAddAttachment()
                         }
 
                         override fun onExpandOrCompactChange() {