Use RTE TextView for timeline text messages, add mention pills to messages (#1990)

* Add `formattedBody` to `TimelineItemTextBasedContent`.

This is pre-computed when timeline events are being mapped from the Rust SDK.

* Update `HtmlConverterProvider` styles.

* Improve `MentionSpan` to add missing `@` or `#` if needed

* Replace `HtmlDocument` with the `TextView` based component

* Improve extra padding calculation for timestamp by rounding the float offset result instead of truncating it.

* Remove composer line height workaround

* Use `ElementRichTextEditorStyle` instead of `RichTextEditorDefaults` for the theming

* Use slightly different styles for composer and messages (top/bottom line height discrepancies, mostly).

* Add `formattedBody` to notice and emote events.

---------

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

features/messages/impl/build.gradle.kts

@@ -73,6 +73,7 @@ dependencies {
     implementation(libs.vanniktech.blurhash)
     implementation(libs.telephoto.zoomableimage)
     implementation(libs.matrix.emojibase.bindings)
+    api(libs.matrix.richtexteditor.compose)
 
     testImplementation(libs.test.junit)
     testImplementation(libs.coroutines.test)
@@ -97,6 +98,8 @@ dependencies {
     testImplementation(libs.test.mockk)
     testImplementation(libs.test.junitext)
     testImplementation(libs.test.robolectric)
+    testImplementation(libs.androidx.compose.ui.test.junit)
+    testReleaseImplementation(libs.androidx.compose.ui.test.manifest)
 
     ksp(libs.showkase.processor)
 }