Change queue to embed the consumers

[bogdandrutu]

This PR will facilitate:

1. The implementation of the disabled queue, can be a simpler call into the "batcher" with the done callback setup and block until that is called.
2. The implementation of the disabled batcher becomes trivial, and does not suffer from the limitation that only one reader of the queue is setup. Even though the request was sent async by multiple go-routines, still one reader which may have been a bottleneck.

In a separate PR will try to get rid of readableQueue. Initial version of the PR had "read" as a private func on Queue, but the "unused" linter complain that boundedMemoryQueue.read was unused.

Technically this is a breaking change, but Queue is an experimental API that we allow changes.

[codecov]

Codecov Report

Attention: Patch coverage is 94.37500% with 9 lines in your changes missing coverage. Please review.

Project coverage is 91.30%. Comparing base (eb4f640) to head (27714cb).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
exporter/exporterhelper/internal/queue_sender.go	62.50%	6 Missing and 3 partials ⚠️

❌ Your patch status has failed because the patch coverage (94.37%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12242      +/-   ##
==========================================
- Coverage   91.31%   91.30%   -0.02%     
==========================================
  Files         465      465              
  Lines       25677    25659      -18     
==========================================
- Hits        23448    23427      -21     
- Misses       1814     1816       +2     
- Partials      415      416       +1     

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[dmitryax]

Looks good to me