fix: revert subscription event source stream handling

[n1ru4l]

Description

This reverts the changes for the executor introduced in #5187

Type of change

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• Bug fix (non-breaking change which fixes an issue)

Further comments

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the solution you did and what alternatives you considered, etc...

[changeset-bot]

🦋 Changeset detected

Latest commit: 96780eb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@graphql-tools/executor	Patch

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[github-actions]

🚀 Snapshot Release (alpha)

The latest changes of this PR are available as alpha on npm (based on the declared changesets):

Package	Version	Info
@graphql-tools/executor	1.2.2-alpha-20240311092808-96780eb2f34560b0b7e04f9c03aca63603a0deea	npm ↗︎ unpkg ↗︎

[github-actions]

✅ Benchmark Results

     ✓ no_errors
     ✓ expected_result

     checks.........................: 100.00% ✓ 352       ✗ 0  
     data_received..................: 41 MB   4.1 MB/s
     data_sent......................: 151 kB  15 kB/s
     http_req_blocked...............: avg=3.89µs   min=2.13µs  med=2.58µs   max=192.27µs p(90)=3.66µs   p(95)=3.82µs  
     http_req_connecting............: avg=704ns    min=0s      med=0s       max=123.98µs p(90)=0s       p(95)=0s      
     http_req_duration..............: avg=52.71ms  min=45.85ms med=49.19ms  max=133.31ms p(90)=55.93ms  p(95)=85.17ms 
       { expected_response:true }...: avg=52.71ms  min=45.85ms med=49.19ms  max=133.31ms p(90)=55.93ms  p(95)=85.17ms 
     http_req_failed................: 0.00%   ✓ 0         ✗ 176
     http_req_receiving.............: avg=135.28µs min=95.32µs med=128.53µs max=570.38µs p(90)=150.77µs p(95)=158.66µs
     http_req_sending...............: avg=25.37µs  min=19.77µs med=24.76µs  max=61.42µs  p(90)=30.17µs  p(95)=33.85µs 
     http_req_tls_handshaking.......: avg=0s       min=0s      med=0s       max=0s       p(90)=0s       p(95)=0s      
     http_req_waiting...............: avg=52.55ms  min=45.69ms med=49.04ms  max=132.99ms p(90)=55.77ms  p(95)=84.99ms 
     http_reqs......................: 176     17.578329/s
     iteration_duration.............: avg=56.86ms  min=49.37ms med=53.11ms  max=138.05ms p(90)=62.38ms  p(95)=89.01ms 
     iterations.....................: 176     17.578329/s
     vus............................: 1       min=1       max=1
     vus_max........................: 1       min=1       max=1

[github-actions]

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