[w3c] Re-organize Trace Context extraction

[duncanista]

What does this PR do?

Re organizes our Trace Context extraction from one file to multiple separated files.

Motivation

For #429, it's ideal to have this PR as predecessor in order to ease review.

Testing Guidelines

n/a

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

[codecov-commenter]

Codecov Report

Merging #432 (4a255dc) into main (35295b3) will increase coverage by 0.81%.
Report is 81 commits behind head on main.
The diff coverage is 82.91%.

❗ Current head 4a255dc differs from pull request most recent head 329db45. Consider uploading reports for the commit 329db45 to get more accurate results

@@            Coverage Diff             @@
##             main     #432      +/-   ##
==========================================
+ Coverage   80.35%   81.16%   +0.81%     
==========================================
  Files          36       50      +14     
  Lines        1761     2039     +278     
  Branches      410      466      +56     
==========================================
+ Hits         1415     1655     +240     
- Misses        294      323      +29     
- Partials       52       61       +9     

Files	Coverage Δ
src/constants.ts	100.00% <100.00%> (ø)
src/metrics/enhanced-metrics.ts	91.89% <100.00%> (-0.61%)	⬇️
src/metrics/listener.ts	85.18% <100.00%> (-0.19%)	⬇️
src/runtime/index.ts	100.00% <100.00%> (+100.00%)	⬆️
src/runtime/user-function.ts	7.69% <ø> (+7.69%)	⬆️
src/trace/constants.ts	100.00% <100.00%> (ø)
src/trace/context/extractors/app-sync.ts	100.00% <100.00%> (ø)
src/trace/context/extractors/step-function.ts	100.00% <100.00%> (ø)
src/trace/trace-context-service.ts	83.33% <100.00%> (-0.54%)	⬇️
src/trace/tracer-wrapper.ts	80.48% <100.00%> (ø)
... and 23 more

... and 1 file with indirect coverage changes

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