Use tags from status when adding handlers to hashtag spans in status content (#2344)

* Migrate LinkHelper to kotlin

* Support tags field on statuses

* Use embedded tags list in status instead of text scraping to embed tag click handler.
Fixes #2283

* Make mentions and tags lists nonnullable

* Make LinkHelper.openLink a Context extension method

* Use builtin extension for uri conversion

* More cleanup in LinkHelper

* Add tests for LinkHelper.getDomain

* Unbreak tags in places that don't have a tag list (e.g. profiles)

* Fixup javadoc

app/src/main/java/com/keylesspalace/tusky/entity/HashTag.kt

@@ -1,3 +1,3 @@
 package com.keylesspalace.tusky.entity
 
-data class HashTag(val name: String)
+data class HashTag(val name: String, val url: String)

app/src/main/java/com/keylesspalace/tusky/entity/Status.kt

@@ -42,6 +42,7 @@ data class Status(
     val visibility: Visibility,
     @SerializedName("media_attachments") var attachments: ArrayList<Attachment>,
     val mentions: List<Mention>,
+    val tags: List<HashTag>,
     val application: Application?,
     val pinned: Boolean?,
     val muted: Boolean?,