Auto generate dark mode previews and screenshots (#776)

With this change, composable previews and screenshots should be created with just:
```
@ElementPreviews
@Composable
fun MyViewPreview() {
    ElementPreview { 
        MyView()
    }
}
```

- Adds `@ElementPreviews` which is a shorthand for:
```
@Preview(name = "D")
@Preview(name = "N", uiMode = Configuration.UI_MODE_NIGHT_YES)
```
Should be used in connection with the now public `fun ElementPreview()` composable.

- Adds ElementPreviews to previewAnnotations in dangerfile
- Screenshots of night mode previews are now rendered with night mode
- Replaces `ElementPreviewLight` and `ElementThemedPreview` with `ElementPreview`
- Deprecates `ElementPreviewDark` which should be removed.
- Remaining usages of `ElementPreviewDark` are now ignored during screenshot tests

services/apperror/impl/src/main/kotlin/io/element/android/services/apperror/impl/AppErrorView.kt

@@ -17,10 +17,10 @@
 package io.element.android.services.apperror.impl
 
 import androidx.compose.runtime.Composable
-import androidx.compose.ui.tooling.preview.Preview
+import io.element.android.libraries.designsystem.preview.ElementPreviews
 import io.element.android.libraries.designsystem.components.dialogs.ErrorDialog
+import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.ElementPreviewDark
-import io.element.android.libraries.designsystem.preview.ElementPreviewLight
 import io.element.android.services.apperror.api.AppErrorState
 import io.element.android.services.apperror.api.aAppErrorState
 
@@ -50,11 +50,13 @@ fun AppErrorViewContent(
     )
 }
 
-@Preview
+@ElementPreviews
 @Composable
-internal fun AppErrorViewLightPreview() = ElementPreviewLight { ContentToPreview() }
+internal fun AppErrorViewLightPreview() {
+    ElementPreview { ContentToPreview() }
+}
 
-@Preview
+@ElementPreviews
 @Composable
 internal fun AppErrorViewDarkPreview() = ElementPreviewDark { ContentToPreview() }