fix not fully defined error

[shenchucheng]

Features

• import Environment in TYPE_CHECKING mode
• fix Role not fully defined error accounting to https://stackoverflow.com/questions/63420889/fastapi-pydantic-circular-references-in-separate-files

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (19b5ede) 80.41% compared to head (caffcf0) 36.73%.

Files	Patch %	Lines
metagpt/roles/role.py	87.50%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff             @@
##              dev     #832       +/-   ##
===========================================
- Coverage   80.41%   36.73%   -43.69%     
===========================================
  Files         200      200               
  Lines       11039    11040        +1     
===========================================
- Hits         8877     4055     -4822     
- Misses       2162     6985     +4823     

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