RSDK-14588 Add a FrameSystem service type and client

[JohnN193]

Problem

The Python SDK has no frame system service type. Frame system access exists only as RPC wrappers on RobotClient, so a module or client that only needs poses has to hold a full RobotClient. In Go the frame system is an RDK internal resource with API rdk-internal:service:frame_system and public name $framesystem, reachable through framesystem.FromDependencies and framesystem.FromProvider.

Depends on #1270 (RobotClient.get_pose).

Change

New package src/viam/services/framesystem/, following the motion service layout:

• FrameSystem(ServiceBase) with API = API("rdk-internal", "service", "frame_system") and PUBLIC_NAME = "$framesystem". Abstract get_frame_system_config, get_pose, transform_pose, transform_pcd, mirroring the RobotClient signatures plus timeout. CurrentInputs is left for RSDK-14593.
• FrameSystem.from_robot(robot) defaults the name to $framesystem. FrameSystem.from_dependencies(deps) looks the frame system up in a dependency mapping and raises ResourceNotFoundError when missing.
• FrameSystemClient(name, channel) over RobotServiceStub. Client only: the RPCs live on RobotService and viam-server owns the implementation, so there is no RPC service and no Registry.register_api. transform_pcd keeps calling the TransformPCD RPC rather than transforming locally, since Python has no point cloud library.
• RESOURCE_NAMESPACE_RDK_INTERNAL = "rdk-internal" added next to RESOURCE_NAMESPACE_RDK.

The ticket left open whether RobotClient.get_service should special case $framesystem the way Go RobotClient.ResourceByName does. Decided yes: RobotClient holds one FrameSystemClient over its own channel, get_service returns it for the reserved name, and the client's channel is reset alongside the robot stub on reconnect. $framesystem never appears in ResourceNames, so the registry lookup is bypassed only for that exact name. Any other name under the API still raises ResourceNotFoundError.

Tests

tests/test_framesystem_service.py against the shared RobotService fixture from tests/test_robot.py, which gains a TransformPCD handler:

• API string, public name and resource_name_from_string("rdk-internal:service:frame_system/$framesystem") round trip.
• FrameSystemClient for all four RPCs, including request field pass through, timeout propagation and reset_channel.
• RobotClient.get_service special case: not in resource_names, returns the same cached client each time, type mismatch still raises ValueError, other names still raise ResourceNotFoundError.
• FrameSystem.from_robot and from_dependencies.

make lint, pyright and make test pass (907 passed, 5 skipped).

Jira: RSDK-14588

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