Async logs - evaluate future inside the executor context

[sampathweb]

Move the future evaluation to inside the with Executor context in which its created.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 78.96%. Comparing base (6d569e4) to head (e79c3ee).

Files with missing lines	Patch %	Lines
keras/src/trainers/trainer.py	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20266      +/-   ##
==========================================
- Coverage   78.96%   78.96%   -0.01%     
==========================================
  Files         505      505              
  Lines       48005    48006       +1     
  Branches     8839     8840       +1     
==========================================
  Hits        37906    37906              
  Misses       8294     8294              
- Partials     1805     1806       +1     

Flag	Coverage Δ
keras	78.81% <75.00%> (-0.01%)	⬇️
keras-jax	62.22% <75.00%> (-0.01%)	⬇️
keras-numpy	57.37% <75.00%> (-0.01%)	⬇️
keras-tensorflow	63.61% <75.00%> (-0.01%)	⬇️
keras-torch	62.27% <75.00%> (-0.01%)	⬇️

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[sampathweb]

Deleting this PR since its addressed offline.