feat: pass rawHeaders

[MoLow]

add rawHeaders whenever we return headers.
hope this PR makes sense
closes #1213

[codecov-commenter]

Codecov Report

Merging #1240 (4b41072) into main (b081930) will increase coverage by 0.19%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1240      +/-   ##
==========================================
+ Coverage   93.87%   94.07%   +0.19%     
==========================================
  Files          43       43              
  Lines        4052     4066      +14     
==========================================
+ Hits         3804     3825      +21     
+ Misses        248      241       -7     

Impacted Files	Coverage Δ
lib/api/api-connect.js	100.00% <100.00%> (ø)
lib/api/api-pipeline.js	100.00% <100.00%> (ø)
lib/api/api-request.js	100.00% <100.00%> (ø)
lib/api/api-stream.js	100.00% <100.00%> (ø)
lib/api/api-upgrade.js	100.00% <100.00%> (ø)
lib/core/util.js	98.47% <100.00%> (+0.01%)	⬆️
lib/fetch/request.js	85.47% <0.00%> (+2.90%)	⬆️

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[ronag]

I'm concerned that this causes reduced performance for an edge case.

[ronag]

Can we make this an option on the request instead? i.e. whether or not to return raw headers. That way it doesn't affect performance and you get exactly what you want in the fastest way possible.

e.g.

    const {
        statusCode,
        headers, // rawHeaders
        trailers,
        body
    } = await undici.request('http://url', { responeHeaders: 'raw' });

I'm not sure what the option should be called but I think something like this.

[MoLow]

Can we make this an option on the request instead? i.e. whether or not to return raw headers. That way it doesn't affect performance and you get exactly what you want in the fastest way possible.

e.g.

    const {
        statusCode,
        headers, // rawHeaders
        trailers,
        body
    } = await undici.request('http://url', { responeHeaders: 'raw' });

I'm not sure what the option should be called but I think something like this.

@ronag makes sense to me,

[mcollina]

lgtm