Don't show the uninstall button when it's noop

This applies to ostree and fwupd resources as well as packagekit's
system update mock one.

BUG: 436365

discover/qml/InstallApplicationButton.qml

@@ -41,6 +41,7 @@ ConditionalLoader
             name: application.isInstalled ? "edit-delete" : "download"
             color: !enabled ? Kirigami.Theme.backgroundColor : !listener.isActive ? (application.isInstalled ? Kirigami.Theme.negativeTextColor : Kirigami.Theme.positiveTextColor) : Kirigami.Theme.backgroundColor
         }
+        visible: listener.isActive || !application.isInstalled || application.isRemovable
         enabled: !listener.isActive && root.isStateAvailable
         onTriggered: root.click()
     }

libdiscover/backends/FwupdBackend/FwupdResource.h

@@ -115,6 +115,10 @@ public:
     }
 
     QString cacheFile() const;
+    bool isRemovable() const override
+    {
+        return false;
+    }
 
 private:
     void setDeviceDetails(FwupdDevice *device);

libdiscover/backends/PackageKitBackend/PackageKitUpdater.cpp

@@ -102,6 +102,10 @@ public:
     {
         return Technical;
     }
+    bool isRemovable() const override
+    {
+        return false;
+    }
 
     QVector<PackageKitResource *> withoutDuplicates() const
     {

libdiscover/backends/RpmOstreeBackend/RpmOstreeResource.h

@@ -42,6 +42,10 @@ public:
     {
         return QList<PackageState>();
     }
+    bool isRemovable() const override
+    {
+        return false;
+    }
     QString availableVersion() const override;
     void setNewVersion(QString);
     QString installedVersion() const override;
@@ -115,4 +119,4 @@ private:
     QDate m_releaseDate;
 };
 
-#endif
\ No newline at end of file
+#endif

libdiscover/resources/AbstractResource.h

@@ -69,6 +69,7 @@ class DISCOVERCOMMON_EXPORT AbstractResource : public QObject
     Q_PROPERTY(QString author READ author CONSTANT)
     Q_PROPERTY(QDate releaseDate READ releaseDate NOTIFY versionsChanged)
     Q_PROPERTY(QString upgradeText READ upgradeText NOTIFY versionsChanged)
+    Q_PROPERTY(bool isRemovable READ isRemovable CONSTANT)
 public:
     /**
      * This describes the state of the resource
@@ -215,6 +216,14 @@ public:
 
     virtual QString upgradeText() const;
 
+    /**
+     * @returns whether the package can ever be removed
+     */
+    virtual bool isRemovable() const
+    {
+        return true;
+    }
+
 public Q_SLOTS:
     virtual void fetchScreenshots();
     virtual void fetchChangelog() = 0;