Increase UT coverage

[disa6302]

Issue #, if available:

What was changed?

• Removed samples and jsmn from coverage report
• Added new unit tests for LWS, Curl, AwsV4Signer and IoT paths
• Fixed typos in the code that were caught while adding new unit tests
• Using lcov instead of gcov to allow for better filters in coverage reports (for our purpose, remove jsmn.h from report).

Why was it changed?

• To ensure existing APIs were tested via unit tests
• To report the appropriate coverage provided by the unit tests

How was it changed?

• Increased test suite
• Moved to lcov to allow for better filtering in the future.
• Increased coverage from 64.24% to 90.81%

What testing was done for the changes?

• Ran existing and new unit tests

Future changes:

• Include LWS build on Mac (currently, there are some globals defined in PIC that causes our unit tests to fail when building LWS and CURL at the same time)
• Include IoT tests in Windows (currently, there is an issue on windows where the SDK cannot open the cert file even if it exists, needs dedicated investigation).

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 90.80%. Comparing base (7f9ff95) to head (1f55db7). Report is 1 commits behind head on develop.

:exclamation: Current head 1f55db7 differs from pull request most recent head 346c5b7. Consider uploading reports for the commit 346c5b7 to get more accurate results

Files	Patch %	Lines
src/source/CallbacksProvider.c	0.00%	1 Missing :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##           develop     #446       +/-   ##
============================================
+ Coverage    63.93%   90.80%   +26.86%     
============================================
  Files           32       28        -4     
  Lines         5077     4894      -183     
============================================
+ Hits          3246     4444     +1198     
+ Misses        1831      450     -1381     

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