RUM-1924: Use tracestate header to supply vendor-specific information

[0xnm]

What does this PR do?

This PR adds tracestate header with Datadog-specific information in case of TRACECONTEXT tracing. This header will contain the following Datadog-specific tags:

• p - parent ID
• s - sampling decision
• o - origin, if exists. In case of instrumentation with RUM, it will have rum value.

Full spec https://www.w3.org/TR/trace-context/#tracestate-header

iOS counterpart DataDog/dd-sdk-ios#1536

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

Merging #1694 (c4a7806) into develop (7e80c37) will decrease coverage by 0.14%.
The diff coverage is 22.92%.

@@             Coverage Diff             @@
##           develop    #1694      +/-   ##
===========================================
- Coverage    83.73%   83.59%   -0.14%     
===========================================
  Files          463      463              
  Lines        15896    15934      +38     
  Branches      2371     2377       +6     
===========================================
+ Hits         13310    13319       +9     
- Misses        1951     1978      +27     
- Partials       635      637       +2     

Files	Coverage Δ
...datadog/android/okhttp/trace/TracingInterceptor.kt	82.03% <91.67%> (+1.39%)	⬆️
.../datadog/opentracing/propagation/W3CHttpCodec.java	3.30% <0.00%> (-1.88%)	⬇️

... and 16 files with indirect coverage changes