feat: Add support for custom COAP requests logging

[akolosov-n]

Introduce a decorator for CoapTransport which logs all inbound and outbound CoAP packets.

The change makes also possible to enable/disable transport logging on CoapServer creation.

[codecov]

Codecov Report

Attention: Patch coverage is 61.70213% with 18 lines in your changes missing coverage. Please review.

Project coverage is 93.01%. Comparing base (7fd3715) to head (592e189).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
.../com/mbed/coap/transport/LoggingCoapTransport.java	69.69%	8 Missing and 2 partials ⚠️
...n/java/com/mbed/coap/server/CoapServerBuilder.java	50.00%	4 Missing and 1 partial ⚠️
.../com/mbed/coap/server/CoapServerBuilderForTcp.java	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #99      +/-   ##
============================================
- Coverage     93.18%   93.01%   -0.17%     
- Complexity     2028     2033       +5     
============================================
  Files           134      134              
  Lines          4577     4598      +21     
  Branches        618      617       -1     
============================================
+ Hits           4265     4277      +12     
- Misses          171      177       +6     
- Partials        141      144       +3     

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[szysas]

Could we name it somehow different, 'request' might be misleading depends on client or server. How about inboundFilter or inboundPreFilter as it happens quite early in a filter pipeline.

[akolosov-n]

Isn't it enough to call it inboundRequestFilter like it is now or e.g. serverRequestFilter? There is CoapRequestConverter in the beginning of the inboundService filter chain which always makes CoapRequests out of the incoming packets meaning that only requests can come into this filter. Calling it just inboundPreFilter makes a feeling that it accepts raw coap packets.