FI-3637: Add fetch bundle resources to core

[vanessuniq]

Summary

This PR adds the fetch_all_bundled_resources method to the FHIR Client DSL, to retrieve FHIR resources from a given bundle. A shared example spec has also been added to ensure method integrity by verifying that fetch_all_bundled_resources is not overridden in subclasses. This helps maintain consistency and prevents unintended redefinition of the method in test kits.

Testing Guidance

[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 84.30%. Comparing base (4331857) to head (c2f6bd2).

Files with missing lines	Patch %	Lines
lib/inferno/dsl/fhir_client.rb	91.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #599      +/-   ##
==========================================
+ Coverage   84.28%   84.30%   +0.01%     
==========================================
  Files         274      274              
  Lines       11603    11627      +24     
  Branches     1295     1303       +8     
==========================================
+ Hits         9780     9802      +22     
- Misses       1815     1817       +2     
  Partials        8        8              

Flag	Coverage Δ
backend	92.62% <91.66%> (-0.01%)	⬇️
frontend	79.11% <ø> (ø)

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