chore: avoid unneeded context.with in http instrumentation

[Flarna]

Avoid the overhead of context.with() by directly passing the extracted context to tracer.startSpan().
This ensures also that the extracted context is not accidentally propagated out of the HTTP instrumentation.

[codecov]

Codecov Report

Merging #2043 (080eba7) into main (9fc1b10) will decrease coverage by 0.02%.
The diff coverage is 91.17%.

❗ Current head 080eba7 differs from pull request most recent head 85ae37d. Consider uploading reports for the commit 85ae37d to get more accurate results

@@            Coverage Diff             @@
##             main    #2043      +/-   ##
==========================================
- Coverage   92.76%   92.74%   -0.03%     
==========================================
  Files         137      137              
  Lines        4904     4904              
  Branches     1012     1013       +1     
==========================================
- Hits         4549     4548       -1     
- Misses        355      356       +1     

Impacted Files	Coverage Δ
...ges/opentelemetry-instrumentation-http/src/http.ts	95.61% <91.17%> (ø)
...emetry-core/src/platform/node/RandomIdGenerator.ts	87.50% <0.00%> (-6.25%)	⬇️