libcamera: value_node: Add mutable adapters

The ValueNode class was initially designed to store read-only property
trees. It is useful to also provide mutable access. Add non-const
adapters and iterators and adapters. This allows obtaining a mutable
ValueNode instance when traversing a tree.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>

src/libcamera/value_node.cpp

@@ -337,6 +337,11 @@ template struct ValueNode::Accessor<std::vector<uint32_t>>;
 template struct ValueNode::Accessor<std::vector<std::string>>;
 #endif /* __DOXYGEN__ */
 
+/**
+ * \fn ValueNode::asDict()
+ * \copydoc ValueNode::asDict() const
+ */
+
 /**
  * \fn ValueNode::asDict() const
  * \brief Wrap a dictionary ValueNode in an adapter that exposes iterators
@@ -357,6 +362,11 @@ template struct ValueNode::Accessor<std::vector<std::string>>;
  * \return An adapter of unspecified type compatible with range-based for loops
  */
 
+/**
+ * \fn ValueNode::asList()
+ * \copydoc ValueNode::asList() const
+ */
+
 /**
  * \fn ValueNode::asList() const
  * \brief Wrap a list ValueNode in an adapter that exposes iterators