feat(instrumenation-document-load): Add custom attributes to document load

[Abinet18]

Which problem is this PR solving?

Adding custom attributes to the Document load instrumentation spans (documentLoad, documentFetch, resourceFetch)
Cloned from #1238

Short description of the changes

This adds a configuration to the document load instrumentation which takes a map of span type to a function that can access the corresponding span and add some attributes to it. By providing the function as a config while registering the DocumentLoad instrumentation will allow for such addition of some vendor specific attributes to the spans.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Abinet18 (31fa293)
• ✅ login: mhassan1 / name: Marc Hassan (1a46b04)

[Abinet18]

@dyladan , @MSNev Can you review this PR instead of the previous one which I abandoned to have a clean start.

[martinkuba]

Could this not be accomplished by using a custom processor?

[Abinet18]

I see that this can be achieved with custom processors. The difference is that with custom processor , all spans will have to be intercepted and modified accordingly , filtering based on some span properties. This will only apply to document load instrumentation spans. There is a similar implementation for fetch and xhr to add custom attributes. If using custom processors is the choice for all scenarios, we may have to deprecate the fetch and xhr apply custom attributes functionality too.

[martinkuba]

I see, makes sense since there is already a precedence for this.

All the other instrumentations use the name applyCustomAttributesOnSpan. I would recommend that we use the same name for consistency.

[Abinet18]

Can this be merged ?

[codecov]

Codecov Report

Merging #1414 (9ab5257) into main (278ba99) will increase coverage by 0.06%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1414      +/-   ##
==========================================
+ Coverage   96.06%   96.13%   +0.06%     
==========================================
  Files          14       14              
  Lines         890      906      +16     
  Branches      192      197       +5     
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+ Hits          855      871      +16     
  Misses         35       35              

Impacted Files	Coverage Δ
...etapackages/auto-instrumentations-web/src/utils.ts	95.83% <100.00%> (ø)
...strumentation-document-load/src/instrumentation.ts	98.98% <100.00%> (+0.19%)	⬆️