fix: icap payload length parsing with atoi FromRadix10

[DanielHaimanot]

avoid using usize::from_radix_10

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.69%. Comparing base (0fded21) to head (507cd2b).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/g3-icap-client/src/reqmod/payload.rs	50.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1074       +/-   ##
===========================================
+ Coverage   23.36%   67.69%   +44.32%     
===========================================
  Files         637     1432      +795     
  Lines       42707   136749    +94042     
===========================================
+ Hits         9979    92571    +82592     
- Misses      32728    44178    +11450     

Flag	Coverage Δ
g3bench	19.75% <0.00%> (?)
g3keymess	20.76% <ø> (ø)
g3mkcert	26.73% <ø> (ø)
g3proxy	49.91% <66.66%> (?)
g3statsd	5.58% <ø> (ø)
lib	57.86% <0.00%> (?)

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