chore: Node tidy

[trisyoungs]

It's a contender for most boring, unreviewable PR of 2026, but here is a Node-wide tidy up PR. The goal was to make all the node definitions consistent in terms of formatting, layout, commenting etc. Bit OCD, but it's done now! I have also removed commented code and a few other small bits of unused / irrelevant stuff here and there, and done a little bit of renaming, but nothing of note.

All the Nodes now look like this:

class MyNode : public Node
{
    public:
    MyNode(Graph *parentGraph);
    ~MyNode() override = default;

    /*
     * Definition
     */
    public:
    // Return type of the node
    std::string_view type() const override;
    // Return short summary of the node's purpose
    std::string_view summary() const override;

    /*
     * Data
     */
    private:
    /* Specific inputs, options, outputs, and data generated by the node

    public:
    // Clear any local data
    void clearData() override;      /* If required, typically analysis nodes, plus GR, SQ etc. */

    /*
     * Processing
     */
    private:
    /* Local functions implemented by the node */

    protected:
    // Perform processing
    NodeConstants::ProcessResult process() override;
};

[RobBuchananCompPhys]

Very cool, glad to see those nodes broken out of sub-dirs too!