fix(tracer): mypy generic to preserve decorated method signature

[heitorlessa]

Issue #, if available: #465

Description of changes:

Checklist

• Meet tenets criteria
• PR title follows conventional commit semantics
• Use generic callable upper bound to preserve signature for type checker (mypy)
• Use generic awaitable upper bound to preserve signature for type checker (mypy)
  • See limitation

Breaking change checklist

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #529 (8e1b352) into develop (5b87bb1) will decrease coverage by 0.04%.
The diff coverage is 83.33%.

@@             Coverage Diff             @@
##           develop     #529      +/-   ##
===========================================
- Coverage    99.23%   99.19%   -0.05%     
===========================================
  Files          113      113              
  Lines         4468     4476       +8     
  Branches       243      243              
===========================================
+ Hits          4434     4440       +6     
- Misses          22       24       +2     
  Partials        12       12              

Impacted Files	Coverage Δ
aws_lambda_powertools/tracing/tracer.py	98.95% <83.33%> (-1.05%)	⬇️

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[heitorlessa]

Limitation: Async functions signature for type checking can only be preserved by using ParamSpec introduced in 3.10 - PEP 612

We could bring typing_extensions module (240K) which also brings other fixes we'll likely encounter as we adopt mypy more broadly in this lib, including nice features like Protocol for interfaces.

I'll postpone bringing typing_extensions until we either a) hear directly from customers using mypy with async fn as this will manifest elsewhere too not just Powertools, or b) find that we need typing_extensions in order to resolve current mypy findings someplace else.

cc @michaelbrewer @pcolazurdo @cakepietoast