Rename BatchTimeout to ScheduleDelay

[sincejune]

This PR renamed BatchTimeout to ScheduleDelay according to the specification: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.6.x/specification/sdk-environment-variables.md#batch-span-processor

Relates to #2515

[codecov]

Codecov Report

Merging #2564 (b4b468f) into main (3cf35bd) will decrease coverage by 0.0%.
The diff coverage is 83.3%.

@@           Coverage Diff           @@
##            main   #2564     +/-   ##
=======================================
- Coverage   76.0%   76.0%   -0.1%     
=======================================
  Files        174     174             
  Lines      12091   12091             
=======================================
- Hits        9194    9190      -4     
- Misses      2652    2656      +4     
  Partials     245     245             

Impacted Files	Coverage Δ
.../otlp/otlptrace/internal/otlptracetest/otlptest.go	0.0% <0.0%> (ø)
sdk/trace/batch_span_processor.go	80.2% <100.0%> (-1.9%)	⬇️

[Aneurysm9]

This would break a stable API and cannot be accepted. An additional option could be added that is synonymous, but we cannot remove the existing option.

[MrAlias]

This would break a stable API and cannot be accepted. An additional option could be added that is synonymous, but we cannot remove the existing option.

Agreed. I would not even recommend adding an additional option as the specification makes no statements requiring or recommending variable or options be named with a particular value. It does specify the environment variable name we need to support, but that is not the same as specifying a name for internal code.

It would be nice to have our names match the specification, but given our stable status and the added confusion of having two options for the same function I am not in favor of accepting changes to the name.