fix(ecs): use threads for describing task definitions

[MrCloudSec]

Description

Use threading for __describe_task_definition__ function to improve the performance of ECS service.

Checklist

• Are there new checks included in this PR? Yes / No
  • If so, do we need to update permissions for the provider? Please review this carefully.
• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[drewkerrigan]

Makes sense to speed this up, thanks @sergargar !

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.86%. Comparing base (eed8f30) to head (146466e).
Report is 232 commits behind head on v3.

Additional details and impacted files

@@            Coverage Diff             @@
##               v3    #4733      +/-   ##
==========================================
- Coverage   86.86%   86.86%   -0.01%     
==========================================
  Files         714      714              
  Lines       22494    22493       -1     
==========================================
- Hits        19539    19538       -1     
  Misses       2955     2955              

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