McuSupport: Store macros as part of McuSdkRepository

To support extending the macros and calling the
McuTargetFactory::expandVariables function statically, the macros are
added as part of the SdkRepository.

This commit also adds helper functions to extend macros other than the
ones created from the packages.

Change-Id: Ie7d2a9ad626782eec18738bdd3472ffd202e7a36
Reviewed-by: Rainer Keller <Rainer.Keller@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/mcusupport/mcuhelpers.h

@@ -14,4 +14,18 @@ struct McuTargetDescription;
 McuTarget::OS deduceOperatingSystem(const McuTargetDescription &);
 QString removeRtosSuffix(const QString &environmentVariable);
 
+template<typename T>
+class asKeyValueRange
+{
+public:
+    asKeyValueRange(T &data)
+        : m_data{data}
+    {}
+    auto begin() { return m_data.keyValueBegin(); }
+    auto end() { return m_data.keyValueEnd(); }
+
+private:
+    T &m_data;
+};
+
 } // namespace McuSupport::Internal