FM2-595: Add support for XML patching operations - AllergyIntolerance Resource

[mherman22]

Description of what I changed

This pull request introduces integration tests for the XML PATCHing operations on the Allergy Intolerance Resource.

For example the xml document below should be supported:

<diff xmlns:fhir="http://hl7.org/fhir"> 
      <replace sel="/fhir:AllergyIntolerance/fhir:category/@value">
         food
      </replace>
</diff>

Issue I worked on

see https://issues.openmrs.org/browse/FM2-595

Checklist: I completed these to help reviewers :)

• My IDE is configured to follow the code style of this project.

  No? Unsure? -> configure your IDE, format the code and add the changes with git add . && git commit --amend

• I have added tests to cover my changes. (If you refactored
  existing code that was well tested you do not have to add tests)

  No? -> write tests and add them to this commit git add . && git commit --amend

• I ran mvn clean package right before creating this pull request and
  added all formatting changes to my commit.

  No? -> execute above command

• All new and existing tests passed.

  No? -> figure out why and add the fix to your commit. It is your responsibility to make sure your code works.

• My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (3958d99) 77.39% compared to head (68ef698) 77.39%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #496   +/-   ##
=========================================
  Coverage     77.39%   77.39%           
  Complexity     2631     2631           
=========================================
  Files           244      244           
  Lines          7381     7381           
  Branches        908      908           
=========================================
  Hits           5712     5712           
  Misses         1126     1126           
  Partials        543      543           

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