Support HX5-D20 XM335 devices on Humble

[HS-P]

Summary

This adds the missing HX5-D20 XM335 model metadata needed by the ROS 2 Humble branch and adjusts the read path used during HX5-D20 bringup.

• Add model table entries for XM335-T332 and XM335-T323.
• Add xm335_t332.model and xm335_t323.model control table definitions.
• Avoid grouped sync-read handling for one-device read transactions by using direct readTxRx.
• Disable fast read by default for this Humble path.

Why

While bringing up an HX5-D20 right hand on ROS 2 Humble, the Dynamixel hardware interface failed against the actual hardware even though DYNAMIXEL Wizard detected and controlled the full device chain correctly.

The observed device layout was:

• ID 110: HX5-D20-MRT
• IDs 111-114, 116-119, 121-124, 126-129, 131-134: XM335-T323
• IDs 115, 120, 125, 130, 135: HX-SENSOR-TIP

The Humble model list did not include model number 1710, so the interface reported:

Cannot find the DXL model from file list (model_num: 1710, model_name: unknown)

After adding the model definition, bringup progressed further but the HX5-D20-MRT read transaction still failed when the read group contained only ID 110:

FastSyncRead Rx Fail [Dxl Size : 1] [Error code : -3001]
Dynamixel Read Fail
Dynamixel Write Fail

For the single-device MRT read case, direct protocol read succeeds and avoids requiring fast/group sync-read support from that one target.

Impact

This allows the Humble branch to recognize the XM335-T323 devices used in HX5-D20 and avoids a bringup-time read failure on the HX5-D20-MRT controller path.

The existing grouped sync-read path remains used for multi-device reads.

Validation

Built locally on ROS 2 Humble:

colcon build --symlink-install --packages-select dynamixel_hardware_interface robotis_hand_bringup robotis_hand_description robotis_hand_pressure_broadcaster --allow-overriding dynamixel_hardware_interface

Validated against an HX5-D20 right hand at 4 Mbps on /dev/ttyUSB0; the model table now resolves model 1710 as xm335_t323.model, and the bringup no longer stops at the missing-model or single-device fast sync read failure.

[gemini-code-assist]

Code Review

This pull request disables the fast read protocol by default, adds model definitions for Dynamixel xm335_t332 and xm335_t323, and optimizes GetDxlValueFromSyncRead by implementing a direct read path when only a single item is being read. Feedback on the implementation suggests capturing the read data item by const reference rather than copying it by value to prevent unnecessary memory allocations in a real-time control loop.

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[gemini-code-assist]

The RWItemList struct contains several std::vector and std::string members. Copying it by value here introduces unnecessary memory allocations and overhead, which is particularly undesirable in a real-time controller loop. Consider capturing it by const reference instead.

    const auto & it_read_data = read_data_list_.front();