[BugReport] Multiple issues with domain randomization and task asset availability

[RobertCHU01]

I've encountered three issues while working with the project:

Issue 1: Domain randomization parameter error causes failure with multiple environments

File: 12_domain_randomization.py
Problem: The script uses an incorrect parameter name num_handlers instead of num_envs. And when num_env > 2, the script fails.

Expected behavior: The script should work correctly with multiple parallel environments.

Issue 2: Missing Maniskill task assets on Hugging Face

Problem: Maniskill tasks are missing all required assets from the Hugging Face repository. This severely limits which tasks can be executed successfully.
Current status: Only two cube-based tasks work:

"pick cube"
"stack cube"

Impact: All other Maniskill tasks cannot run due to missing assets.

Expected behavior: All Maniskill tasks should have their assets available on Hugging Face for download and execution.

Issue 3: RLBench tasks

Problem: Many Rlbench asset objects do not have collision prim, causing some objects to sink into the ground or disappear from the video.
Current status: Only cube-based tasks and articulated-object (which is built on cube) based tasks work:

[RobertCHU01]

Issue 3: RLBench tasks (Continued)

Most of the RLBench task files are missing a success checker at the end, though there's already a TODO.