Rewrite media caching (old image provider)

- Doesn't use pyotherside's image provider feature, for more flexibility
  and simplicity
- Suitable for supporting matrix media events and more later
- Avoid a lot of duplicate files that the old cache created due to
  server not returning what we expect, mistakes in Python/QML code, etc
- Changed file structure
  (e.g. thumbnails/32x32/<mxc id> instead of
   thumbnails/<mxc id>.32.32.crop)

- Backend.wait_until_account_exist: start issuing warnings if the
  function runs for more than 10s, which means in most case a bad user
  ID was passed

- New HMxcImage QML component, used in H(User/Room)Avatar

src/qml/Chat/Banners/Banner.qml

@@ -36,6 +36,7 @@ Rectangle {
 
                 HUserAvatar {
                     id: bannerAvatar
+                    clientUserId: chatPage.userId
                     anchors.centerIn: parent
                 }
             }

src/qml/Chat/Banners/InviteBanner.qml

@@ -11,7 +11,7 @@ Banner {
 
     avatar.userId: inviterId
     avatar.displayName: inviterName
-    avatar.avatarUrl: inviterAvatar
+    avatar.mxc: inviterAvatar
 
     labelText: qsTr("%1 invited you to this room.").arg(
         Utils.coloredNameHtml(inviterName, inviterId)

src/qml/Chat/Banners/LeftBanner.qml

@@ -8,7 +8,7 @@ Banner {
     // TODO: avatar func auto
     avatar.userId: chatPage.userId
     avatar.displayName: chatPage.userInfo.display_name
-    avatar.avatarUrl: chatPage.userInfo.avatar_url
+    avatar.mxc: chatPage.userInfo.avatar_url
     labelText: qsTr("You are not part of this room anymore.")
 
     buttonModel: [

src/qml/Chat/Composer.qml

@@ -58,9 +58,10 @@ Rectangle {
 
         HUserAvatar {
             id: avatar
+            clientUserId: chatPage.userId
             userId: writingUserId
             displayName: writingUserInfo.display_name
-            avatarUrl: writingUserInfo.avatar_url
+            mxc: writingUserInfo.avatar_url
         }
 
         HScrollableTextArea {

src/qml/Chat/RoomHeader.qml

@@ -23,8 +23,9 @@ Rectangle {
 
         HRoomAvatar {
             id: avatar
+            clientUserId: chatPage.userId
             displayName: chatPage.roomInfo.display_name
-            avatarUrl: chatPage.roomInfo.avatar_url
+            mxc: chatPage.roomInfo.avatar_url
             Layout.alignment: Qt.AlignTop
         }
 

src/qml/Chat/RoomSidePane/MemberDelegate.qml

@@ -7,9 +7,12 @@ HTileDelegate {
     backgroundColor: theme.chat.roomSidePane.member.background
 
     image: HUserAvatar {
+        clientUserId: chatPage.userId
         userId: model.user_id
         displayName: model.display_name
-        avatarUrl: model.avatar_url
+        mxc: model.avatar_url
+        width: height
+        height: memberDelegate.height
     }
 
     title.text: model.display_name || model.user_id

src/qml/Chat/Timeline/EventContent.qml

@@ -52,9 +52,10 @@ HRowLayout {
 
         HUserAvatar {
             id: avatar
+            clientUserId: chatPage.userId
             userId: model.sender_id
             displayName: model.sender_name
-            avatarUrl: model.sender_avatar
+            mxc: model.sender_avatar
             width: parent.width
             height: collapseAvatar ? 1 : 58
         }