feat: support parse schema

[xiegx94]

This PR provides a new handler that can parse json for a given schema.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 72.13930% with 56 lines in your changes are missing coverage. Please review.

Project coverage is 73.86%. Comparing base (4250a05) to head (f55bd94).

Files	Patch %	Lines
include/sonic/dom/schema_handler.h	74.64%	5 Missing and 31 partials :warning:
include/sonic/dom/parser.h	57.69%	7 Missing and 4 partials :warning:
include/sonic/dom/generic_document.h	72.72%	4 Missing and 5 partials :warning:

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #85      +/-   ##
==========================================
- Coverage   74.79%   73.86%   -0.93%     
==========================================
  Files          21       22       +1     
  Lines        2436     2629     +193     
  Branches      667      716      +49     
==========================================
+ Hits         1822     1942     +120     
- Misses        297      369      +72     
- Partials      317      318       +1     

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