refactor(sdk-trace-base): make resource private and remove getActiveSpanProcessor API

[david-luna]

Which problem is this PR solving?

Resource and active span processor should not be accessible once the tracer provider is constructed. This PR makes the necessary changes to have both as private properties and inject them into any tracer created via getTracer API.

Fixes #4791
Fixes #4792

Short description of the changes

• made resource private in BasicTracerProvider
• remove getActiveSpanProcessor in BasicTracerProvider
• refactor SpanImpl constructor
• update Tracer.startSpan to use the new constructor
• refactor Tracer constructor to get only necessary deps (processor & resource) instead of the provider
• update tests

Changes in SpanImpl constructor

I've decided to change the constructor method signature for SpanImpl. This way we inject the necessary dependencies that are held in the Tracer class making unnecessary to have public properties or getters for span processor and resource. The class was made private (not exported) in #5048

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

• npm run compile && npm run test

Checklist:

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.13%. Comparing base (4a394cc) to head (ddc574b).
Report is 4 commits behind head on next.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #5192      +/-   ##
==========================================
- Coverage   93.15%   93.13%   -0.03%     
==========================================
  Files         315      315              
  Lines        8113     8102      -11     
  Branches     1633     1633              
==========================================
- Hits         7558     7546      -12     
- Misses        555      556       +1     

Files with missing lines	Coverage Δ
...elemetry-sdk-trace-base/src/BasicTracerProvider.ts	96.26% <100.00%> (+0.57%)	⬆️
packages/opentelemetry-sdk-trace-base/src/Span.ts	97.60% <100.00%> (-0.02%)	⬇️
...ackages/opentelemetry-sdk-trace-base/src/Tracer.ts	98.55% <100.00%> (-0.03%)	⬇️

... and 1 file with indirect coverage changes

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[pichlermarc]

looks good, thanks 👍