Unexport the simple and batch SpanProcessors

[MrAlias]

Resolves #1637

API prior to change:

Post change:

[codecov]

Codecov Report

Merging #1638 (4d0c72b) into main (992837f) will increase coverage by 0.0%.
The diff coverage is 100.0%.

@@          Coverage Diff          @@
##            main   #1638   +/-   ##
=====================================
  Coverage   77.3%   77.3%           
=====================================
  Files        128     128           
  Lines       6671    6669    -2     
=====================================
  Hits        5157    5157           
+ Misses      1267    1265    -2     
  Partials     247     247           

Impacted Files	Coverage Δ
sdk/trace/batch_span_processor.go	78.8% <100.0%> (ø)
sdk/trace/simple_span_processor.go	75.0% <100.0%> (ø)
exporters/trace/jaeger/env.go	100.0% <0.0%> (ø)
exporters/otlp/otlpgrpc/connection.go	88.7% <0.0%> (+1.8%)	⬆️