Expands functionality of FrameTransformer to allow multi-body transforms (#858)

# Description

Update FrameTransformer to handle 2 new functionalities:
* Target frames that aren't children of the source frame prim_path
* Target frames that are based upon the source frame prim_path

These new changes mean that the frame names will most likely be
different than the configured order - but this was always a possibility
to the way the regex is parsed. To be safe, users need to use
`frame_names` to determine indexing into `FrameTransformerData`.

Test cases have been added for both of these new functionalities -
thanks @Mayankm96!

Also, the run script has been updated slightly as the previous indexing
was off by 1.


Fixes #857 #294

## Type of change

- New feature (non-breaking change which adds functionality)

## Checklist

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

source/extensions/omni.isaac.lab/config/extension.toml

 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.24.18"
+version = "0.24.19"
 
 # Description
 title = "Isaac Lab framework for Robot Learning"

source/extensions/omni.isaac.lab/docs/CHANGELOG.rst

 Changelog
 ---------
 
+0.24.19 (2024-10-05)
+~~~~~~~~~~~~~~~~~~~~
+
+Added
+^^^^^
+
+* Added new functionalities to the FrameTransformer to make it more general. It is now possible to track:
+
+  * Target frames that aren't children of the source frame prim_path
+  * Target frames that are based upon the source frame prim_path
+
+
 0.24.18 (2024-10-04)
 ~~~~~~~~~~~~~~~~~~~~
 

source/extensions/omni.isaac.lab/omni/isaac/lab/sensors/frame_transformer/frame_transformer_cfg.py

@@ -31,10 +31,15 @@ class FrameTransformerCfg(SensorBaseCfg):
         """Information specific to a coordinate frame."""
 
         prim_path: str = MISSING
-        """The prim path corresponding to the parent rigid body.
+        """The prim path corresponding to a rigid body.
 
-        This prim should be part of the same articulation as :attr:`FrameTransformerCfg.prim_path`.
+        This can be a regex pattern to match multiple prims. For example, "/Robot/.*" will match all prims under "/Robot".
+
+        This means that if the source :attr:`FrameTransformerCfg.prim_path` is "/Robot/base", and the target :attr:`FrameTransformerCfg.FrameCfg.prim_path` is "/Robot/.*",
+        then the frame transformer will track the poses of all the prims under "/Robot",
+        including "/Robot/base" (even though this will result in an identity pose w.r.t. the source frame).
         """
+
         name: str | None = None
         """User-defined name for the new coordinate frame. Defaults to None.
 

source/extensions/omni.isaac.lab/omni/isaac/lab/sensors/frame_transformer/frame_transformer_data.py

@@ -15,8 +15,8 @@ class FrameTransformerData:
     """Target frame names (this denotes the order in which that frame data is ordered).
 
     The frame names are resolved from the :attr:`FrameTransformerCfg.FrameCfg.name` field.
-    This usually follows the order in which the frames are defined in the config. However, in
-    the case of regex matching, the order may be different.
+    This does not necessarily follow the order in which the frames are defined in the config due to
+    the regex matching.
     """
 
     target_pos_source: torch.Tensor = None

source/standalone/tutorials/04_sensors/run_frame_transformer.py

@@ -139,10 +139,10 @@ def run_simulator(sim: sim_utils.SimulationContext, scene_entities: dict):
             if count % 50 == 0:
                 # get frame names
                 frame_names = frame_transformer.data.target_frame_names
-                print(f"Displaying Frame ID {frame_index}: {frame_names[frame_index]}")
                 # increment frame index
                 frame_index += 1
                 frame_index = frame_index % len(frame_names)
+                print(f"Displaying Frame ID {frame_index}: {frame_names[frame_index]}")
 
             # visualize frame
             source_pos = frame_transformer.data.source_pos_w