Cleaning in envs common.py

[matteobettini]

Description

1. Removed identical set_seed override in _EnvWrapper
2. Updated type hints in set_seed of EnvBase
3. Made _init_env() abstract in _EnvWrapper

Motivation and Context

We now enforce inheritors of _EnvWrapper to implement _init_env()

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

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

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.

I have checked that the tests in test_env.py which I am able to run (without external libraries and cuda) are all passing and linted.

[codecov]

Codecov Report

Merging #769 (d8fa4f3) into main (c15b056) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #769      +/-   ##
==========================================
+ Coverage   88.72%   88.75%   +0.02%     
==========================================
  Files         123      123              
  Lines       20994    20987       -7     
==========================================
  Hits        18626    18626              
+ Misses       2368     2361       -7     

Flag	Coverage Δ
habitat-gpu	24.97% <100.00%> (+0.01%)	⬆️
linux-brax	29.58% <100.00%> (+0.01%)	⬆️
linux-cpu	85.28% <100.00%> (+0.02%)	⬆️
linux-gpu	86.18% <100.00%> (+0.02%)	⬆️
linux-jumanji	30.36% <100.00%> (+0.02%)	⬆️
linux-outdeps-gpu	71.89% <100.00%> (+0.02%)	⬆️
linux-stable-cpu	85.14% <100.00%> (+0.02%)	⬆️
linux-stable-gpu	85.84% <100.00%> (+0.02%)	⬆️
linux_examples-gpu	42.94% <100.00%> (+0.02%)	⬆️
macos-cpu	84.96% <100.00%> (+0.02%)	⬆️
olddeps-gpu	75.93% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
torchrl/envs/common.py	83.33% <100.00%> (+1.46%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[vmoens]

LGTM thanks!