Refactor SidePane ListView in a flat way

Also adjust some colors (accentBackground)

TODO: Repair Filter rooms field

src/qml/SidePane/AccountDelegate.qml

@@ -1,94 +0,0 @@
-import QtQuick 2.12
-import QtQuick.Layouts 1.12
-import "../Base"
-
-Column {
-    id: accountDelegate
-    width: parent.width
-    spacing: theme.spacing / 2
-
-    opacity:
-        paneToolBar.roomFilter && roomList.model.count < 1 ? 0.3 : 1
-    Behavior on opacity { HNumberAnimation {} }
-
-    property alias roomList: roomList
-
-    property bool forceExpand: paneToolBar.roomFilter && roomList.model.count
-    property bool expanded: true
-    readonly property var modelItem: model
-
-    readonly property bool isCurrent:
-        window.uiState.page == "Pages/EditAccount/EditAccount.qml" &&
-        window.uiState.pageProperties.userId == model.user_id
-
-    Component.onCompleted:
-        expanded = ! window.uiState.collapseAccounts[model.user_id]
-
-    onExpandedChanged: {
-        window.uiState.collapseAccounts[model.user_id] = ! expanded
-        window.uiStateChanged()
-    }
-
-    function activate() {
-        pageStack.showPage(
-            "EditAccount/EditAccount", { "userId": model.user_id }
-        )
-    }
-
-    HInteractiveRectangle {
-        id: rectangle
-        width: parent.width
-        height: childrenRect.height
-        color: theme.sidePane.account.background
-
-        checked: accountDelegate.isCurrent
-
-        TapHandler { onTapped: accountDelegate.activate() }
-
-        HRowLayout {
-            id: row
-            width: parent.width
-
-            HUserAvatar {
-                id: avatar
-                userId: model.user_id
-                displayName: model.display_name
-                avatarUrl: model.avatar_url
-            }
-
-            HLabel {
-                id: accountLabel
-                color: theme.sidePane.account.name
-                text: model.display_name || model.user_id
-                font.pixelSize: theme.fontSize.big
-                elide: HLabel.ElideRight
-                leftPadding: sidePane.currentSpacing
-                rightPadding: leftPadding
-
-                Layout.fillWidth: true
-                Layout.fillHeight: true
-            }
-
-            ExpandButton {
-                id: expandButton
-                opacity: paneToolBar.roomFilter ? 0 : 1
-                expandableItem: accountDelegate
-                Layout.preferredHeight: row.height
-            }
-        }
-    }
-
-    RoomList {
-        id: roomList
-        visible: height > 0
-        width: parent.width
-        height:
-            childrenRect.height *
-            (accountDelegate.expanded || accountDelegate.forceExpand ? 1 : 0)
-        clip: heightAnimation.running
-
-        userId: modelItem.user_id
-
-        Behavior on height { HNumberAnimation { id: heightAnimation } }
-    }
-}