Add support to device tree generation support for DT_NODELABEL_<node-label>_<FOO> generation

[galak]

Add support to scripts/dts/gen_defines.py to generate device tree node label based defines. These should be of the form DT_NODELABEL_<node-label>_<FOO>

So for something like:

    soc {
            flash-controller@40020000 {
                    cool_label_name: flash0: flash@0 {
                            flash0_reg: reg = < 0x0 0x100000 >;
                            };
                    };
            };
    };

/* assuming Issue #22554 - DT_PATH_ */
#define DT_NODELABEL_FLASH0_BASE_ADDRESS DT_PATH_SOC_FLASH_CONTROLLER_40020000_BASE_ADDRESS
#define DT_NODELABEL_COOL_LABEL_NAME_BASE_ADDRESS DT_PATH_SOC_FLASH_CONTROLLER_40020000_BASE_ADDRESS

NOTE: We should only generate labels for node's at this time. So the label flash0_reg on a property should NOT generate a define. In the future if we need this we should call it DT_PROP_LABEL_...

[galak]

Need to document as part of this work:

• node labels should ideally get used rarely in the code, should be for true cases that DT_INST defines can't be used because you need to know the actual SoC/HW instance
• If a label is used for SoC identification it should match the SoC Vendor documentation for that device.

[erwango]

Having a DT_NODEL_LABEL_<node-label> will be required to enable following usage

#ifdef DT_NODEL_LABEL_<node-label>
#endif

This will help removing most (all ideally) of #ifdef CONFIG_CAN_1 like macros.

[pabigot]

I would strongly prefer DT_NODELABEL_ as the prefix rather than introduce what appear to be syntactic subelements within the namespace identifier.