added undo-replace-references operation

[mrdnctrk]

closes: #7101

In this PR

1. I added a new system level operation, named $hapi.fhir.undo-replace-references. This operation
   restores the resources that were updated by a $hapi.fhir.replace-references operation to their previous versions.

Current limitations:

• It fails if any resources to be restored have been subsequently changed since the $hapi.fhir.replace-references operation was performed.
• It can only run synchronously.
• It fails if the number of resources to restore exceeds a specified resource limit (currently set by the Provider class to the same size as getInternalSynchronousSearchSize of JPAStorageSettings , which defaults to 10000).

2. I noticed that replace-references operation was creating a Provenance resource even when no resource was updated, so I added logic to prevent it.

3. Also added logic for replace-references Provenances to not add a resource reference to the Provenance if patch for that resource was a no-op ( so the resource was't really updated by the operation). This is not likely to happen under normal conditions but just added as a precaution, since we don't want to revert the resource a previous version if that resource wasn't really updated by replace-references.

4. I refactored the ReplaceReferencesTestHelper by extracting the test data generation and the validation specific to that test data into a separate class called ReplaceReferencesLargeTestData. The reasons for doing this:
   a. make tests more efficient: ReplaceReferencesTestHelper is used by various different test suites, including the tests for replace-references, merge and undo-replace-references operations. However not all tests require the large amount of data created by default in this class.
   b. increase code maintainability/readability.

[robogary]

Formatting check succeeded!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.80%. Comparing base (112cec3) to head (f169380).
Report is 68 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7097      +/-   ##
============================================
+ Coverage     83.41%   83.80%   +0.38%     
- Complexity    29193    29367     +174     
============================================
  Files          1843     1803      -40     
  Lines        113422   113602     +180     
  Branches      14251    14309      +58     
============================================
+ Hits          94608    95201     +593     
+ Misses        12730    12290     -440     
- Partials       6084     6111      +27     

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[volodymyr-korzh]

Looks good, approved