Corrects calculation of target height adjustment based on sensor data

[fan-ziqi]

Description

Corrected calculation of target height adjustment based on sensor data.

Fixes #1546 and #1698

Thanks to @ClemensSchwarke and @shendredm for the modification suggestions. To use this base_height_l2 reward function, users need to make the following changes:

1. Customize a new sensor

class MySceneCfg(InteractiveSceneCfg):
    height_scanner_base = RayCasterCfg(
        prim_path="{ENV_REGEX_NS}/Robot/base",
        offset=RayCasterCfg.OffsetCfg(pos=(0.0, 0.0, 20.0)),
        attach_yaw_only=True,
        pattern_cfg=patterns.GridPatternCfg(resolution=0.05, size=(0.1, 0.1)),
        debug_vis=False,
        mesh_prim_paths=["/World/ground"],
    )

2. Pass this new sensor to the reward function

class RewardsCfg:
    base_height_l2 = RewTerm(
        func=mdp.base_height_l2,
        weight=0.0,
        params={
            "asset_cfg": SceneEntityCfg("robot", body_names=""),
            "sensor_cfg": SceneEntityCfg("height_scanner_base"),
            "target_height": 0.0,
        },
    )

This will create a 10 by 10 cm patch consisting of 9 rays and should provide a good estimate of the ground height at the robot's position.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there