[rust] support handling settings command in Producer

[glcrazier]

Which Issue(s) This PR Fixes

Fixes #634
Fixes #598

Brief Description

I've refactored the way of processing telemetry commands. Now the transaction command from the server is processed in Producer instead of Client. The client with different types can handle telemetry command within its own impl block.

How Did You Test This Change?

run cargo test and example to make sure it works

[codecov-commenter]

Codecov Report

Attention: 76 lines in your changes are missing coverage. Please review.

Comparison is base (65b70ed) 55.89% compared to head (e03f30b) 47.56%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
rust/src/producer.rs	65.90%	41 Missing and 19 partials ⚠️
rust/src/simple_consumer.rs	38.88%	8 Missing and 3 partials ⚠️
rust/src/client.rs	64.28%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #682      +/-   ##
============================================
- Coverage     55.89%   47.56%   -8.34%     
  Complexity      668      668              
============================================
  Files           259      207      -52     
  Lines         15653    12344    -3309     
  Branches       3891     3701     -190     
============================================
- Hits           8750     5872    -2878     
+ Misses         6650     6195     -455     
- Partials        253      277      +24     

Flag	Coverage Δ
nodejs	?
rust	79.32% <63.46%> (+0.01%)	⬆️

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[lizhanhui]

Now things look good