[3.8] Implemented readuntil in StreamResponse (#4734)

[github-actions]

Backports the following commits to 3.8:

• Implemented readuntil in StreamResponse (Implemented readuntil in StreamResponse  #4734)

[codecov]

Codecov Report

Merging #5196 into 3.8 will decrease coverage by 0.02%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##              3.8    #5196      +/-   ##
==========================================
- Coverage   97.55%   97.53%   -0.03%     
==========================================
  Files          44       44              
  Lines        8839     8844       +5     
  Branches     1423     1424       +1     
==========================================
+ Hits         8623     8626       +3     
- Misses        101      102       +1     
- Partials      115      116       +1     

Flag	Coverage Δ
unit	97.53% <85.71%> (-0.03%)	⬇️

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Impacted Files	Coverage Δ
aiohttp/streams.py	97.46% <85.71%> (-0.49%)	⬇️

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