feat(jaeger): remove internal message queue between exporter and exporting tasks

[TommyCpp]

#781 introduced an internal queue between jaeger exporter's export method and uploader that actually handles the exporting because Uploader's upload methods takes a mutable reference and hence cannot be called concurrently.

The internal queue helped unblock #781 but has following problems:

• when sending to collectors we use HTTP clients and those clients are Send + Sync thus the queue is not needed.
• The queue has an arbitrary capacity of 64, if we can concurrently export more than 64 spans it can result in span dropping.

This PR proposes that:

• Make upload takes immutable self so that we can call it concurrently.
• Internally add lock around agent uploader
• Remove the internal queue inside jaeger exporter.

[codecov]

Codecov Report

Merging #848 (337694a) into main (be0e1f6) will increase coverage by 0.0%.
The diff coverage is 34.4%.

@@          Coverage Diff          @@
##            main    #848   +/-   ##
=====================================
  Coverage   68.9%   69.0%           
=====================================
  Files        115     115           
  Lines       9371    9344   -27     
=====================================
- Hits        6462    6452   -10     
+ Misses      2909    2892   -17     

Impacted Files	Coverage Δ
opentelemetry-jaeger/src/exporter/mod.rs	54.6% <18.7%> (+3.3%)	⬆️
opentelemetry-jaeger/src/exporter/uploader.rs	18.7% <20.0%> (-0.7%)	⬇️
...emetry-jaeger/src/exporter/config/collector/mod.rs	58.3% <66.6%> (ø)
opentelemetry-jaeger/src/exporter/config/agent.rs	58.0% <75.0%> (ø)
...aeger/src/exporter/config/collector/http_client.rs	23.0% <100.0%> (ø)
opentelemetry-api/src/context.rs	82.9% <0.0%> (-6.0%)	⬇️
opentelemetry-jaeger/src/exporter/agent.rs	13.4% <0.0%> (+0.9%)	⬆️
opentelemetry-sdk/src/metrics/controllers/push.rs	83.3% <0.0%> (+3.3%)	⬆️
opentelemetry-api/src/trace/mod.rs	76.5% <0.0%> (+4.5%)	⬆️

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[jtescher]

Looks good