fix: pass same context to Sampler and SpanProcessor in root span case

[Flarna]

Which problem is this PR solving?

Currently Sampler gets a different context then SpanProcessor in case option.root is set to true. This is inconsistent and besides that the SpanProcessor might end up in a wrong conclusion regarding parent span which is not intended.

Short description of the changes

If options.root is set the behavior is like no parent span is on context.
Delete a potential span from context and pass this new context to onStart() and shouldSample().

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• see added tests

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

Merging #2790 (7eafa8e) into main (2da6754) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 7eafa8e differs from pull request most recent head dedbaac. Consider uploading reports for the commit dedbaac to get more accurate results

@@            Coverage Diff             @@
##             main    #2790      +/-   ##
==========================================
- Coverage   93.43%   93.42%   -0.01%     
==========================================
  Files         159      159              
  Lines        5452     5449       -3     
  Branches     1145     1143       -2     
==========================================
- Hits         5094     5091       -3     
  Misses        358      358              

Impacted Files	Coverage Δ
...ackages/opentelemetry-sdk-trace-base/src/Tracer.ts	98.38% <100.00%> (-0.08%)	⬇️