Use the concurent batch processor from SDK exporters

[jmacd]

Description: We have several high-volume span producers that will benefit from concurrency.
Meanwhile, the new processor will not harm existing low-volume users, so we use it unconditionally.

Batching parameters have been set to 1000/1500 (batch_size / max_size) and 32MiB in flight.

Link to tracking Issue:
Fixes #568

[jmacd]

LS-54663

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (69c6e8c) 89.41% compared to head (987c178) 89.53%.

❗ Current head 987c178 differs from pull request most recent head 1f01e2e. Consider uploading reports for the commit 1f01e2e to get more accurate results

Files	Patch %	Lines
...htstep/sdk/metric/exporters/otlp/otelcol/client.go	87.50%	1 Missing ⚠️
...ghtstep/sdk/trace/exporters/otlp/otelcol/client.go	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #569      +/-   ##
==========================================
+ Coverage   89.41%   89.53%   +0.11%     
==========================================
  Files          62       62              
  Lines        3600     3602       +2     
==========================================
+ Hits         3219     3225       +6     
+ Misses        287      285       -2     
+ Partials       94       92       -2     

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