feat: exchange code for session now fully async

[silentworks]

What kind of change does this PR introduce?

Bug fix: change exchange_code_for_session to async method

What is the current behavior?

Please link any relevant issues here.

What is the new behavior?

Feel free to include screenshots if it includes visual changes.

Additional context

Add any other context or screenshots.

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (08bada3) 45.40% compared to head (a8afd06) 45.37%.
Report is 2 commits behind head on main.

❗ Current head a8afd06 differs from pull request most recent head a249ba0. Consider uploading reports for the commit a249ba0 to get more accurate results

Files	Patch %	Lines
gotrue/_async/gotrue_client.py	25.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #378      +/-   ##
==========================================
- Coverage   45.40%   45.37%   -0.04%     
==========================================
  Files          23       23              
  Lines        1958     1955       -3     
==========================================
- Hits          889      887       -2     
+ Misses       1069     1068       -1     

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