Plain text editor implementation based on markdown input (#2840)

* Add plain text editor based on markdown input
- Fix autofocus of message composer.
- Remove `Message` data class, fetch the details in `MessagesPresenter` instead.
- Remove `enable rich text` option from advanced settings, set it as a build configuration instead.
* Fix MentionSpanProvider
* Bump RTE library to released `v2.37.3`

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Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/preferences/test/src/main/kotlin/io/element/android/libraries/preferences/test/InMemoryAppPreferencesStore.kt

@@ -21,24 +21,14 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 
 class InMemoryAppPreferencesStore(
-    isRichTextEditorEnabled: Boolean = false,
     isDeveloperModeEnabled: Boolean = false,
     customElementCallBaseUrl: String? = null,
     theme: String? = null,
 ) : AppPreferencesStore {
-    private val isRichTextEditorEnabled = MutableStateFlow(isRichTextEditorEnabled)
     private val isDeveloperModeEnabled = MutableStateFlow(isDeveloperModeEnabled)
     private val customElementCallBaseUrl = MutableStateFlow(customElementCallBaseUrl)
     private val theme = MutableStateFlow(theme)
 
-    override suspend fun setRichTextEditorEnabled(enabled: Boolean) {
-        isRichTextEditorEnabled.value = enabled
-    }
-
-    override fun isRichTextEditorEnabledFlow(): Flow<Boolean> {
-        return isRichTextEditorEnabled
-    }
-
     override suspend fun setDeveloperModeEnabled(enabled: Boolean) {
         isDeveloperModeEnabled.value = enabled
     }