[Feature] Lazy TensorClass storage

[tcbegley]

Description

This PR adds support for tensorclasses to Lazy{Tensor,Memmap}Storage. This should allow us to add support for tensorclasses to replay buffers in future.

[codecov]

Codecov Report

Merging #752 (4761fab) into main (1f8341c) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 4761fab differs from pull request most recent head 741dbdc. Consider uploading reports for the commit 741dbdc to get more accurate results

@@            Coverage Diff             @@
##             main     #752      +/-   ##
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- Coverage   88.77%   88.77%   -0.01%     
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  Files         123      123              
  Lines       20788    20814      +26     
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+ Hits        18454    18477      +23     
- Misses       2334     2337       +3     

Flag	Coverage Δ
habitat-gpu	25.14% <12.50%> (-0.01%)	⬇️
linux-brax	29.48% <12.50%> (-0.02%)	⬇️
linux-cpu	85.31% <100.00%> (+0.01%)	⬆️
linux-gpu	86.22% <100.00%> (+0.01%)	⬆️
linux-jumanji	30.21% <12.50%> (-0.02%)	⬇️
linux-outdeps-gpu	72.10% <100.00%> (+0.03%)	⬆️
linux-stable-cpu	85.16% <100.00%> (+0.01%)	⬆️
linux-stable-gpu	85.86% <100.00%> (+<0.01%)	⬆️
linux_examples-gpu	43.00% <25.00%> (-0.02%)	⬇️
macos-cpu	84.99% <100.00%> (+0.01%)	⬆️
olddeps-gpu	75.96% <100.00%> (+0.03%)	⬆️

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Impacted Files	Coverage Δ
test/test_rb.py	97.43% <100.00%> (+0.10%)	⬆️
torchrl/data/replay_buffers/storages.py	84.05% <100.00%> (+0.56%)	⬆️
torchrl/envs/vec_env.py	69.13% <0.00%> (-0.51%)	⬇️

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[vmoens]

Great work! I added a couple of tests for get and set