Move sdkmanager's sdk level parsing to AndroidConfig

Both the sdkmanger and avdmanager (maybe more) need to parse the sdk
level for packages and devices which may contain letters, make them
use the same logic.

Change-Id: Iff7fef3a66e00fac11b833f73f2f334a4cf1a766
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/android/androidconfigurations.h

@@ -91,6 +91,7 @@ public:
 
     static QStringList apiLevelNamesFor(const SdkPlatformList &platforms);
     static QString apiLevelNameFor(const SdkPlatform *platform);
+    static int platformNameToApiLevel(const QString &platformName);
 
     Utils::FilePath sdkLocation() const;
     void setSdkLocation(const Utils::FilePath &sdkLocation);