Fix test failure related to change in core to add content-encoding to response headers

[cwperks]

Description

Fix test failure related to change in core to add content-encoding to response headers

TBD will link to related change in core

• Category (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation)

Test fix

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

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[cwperks]

Looks related to opensearch-project/OpenSearch#20358 based on the tests that were changed in HttpCompressionIT.

[cwperks]

Pushing a fix to resolve remaining failures:

Tests with failures:
 - org.opensearch.security.dlic.dlsfls.DlsFlsCrossClusterSearchTest.testCcsDifferentConfigBoth
 - org.opensearch.security.dlic.dlsfls.DlsFlsCrossClusterSearchTest.testCcs
 - org.opensearch.security.dlic.dlsfls.DlsFlsCrossClusterSearchTest.testCcsDifferentConfig
 - org.opensearch.security.dlic.dlsfls.DlsFlsCrossClusterMinimalRoundtripSearchTests.testCcsDifferentConfigBoth
 - org.opensearch.security.dlic.dlsfls.DlsFlsCrossClusterMinimalRoundtripSearchTests.testCcs
 - org.opensearch.security.dlic.dlsfls.DlsFlsCrossClusterMinimalRoundtripSearchTests.testCcsDifferentConfig

[cwperks]

Took this opportunity to also refactor with TextBlocks for readability.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.70%. Comparing base (7f168b1) to head (1c8935e).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5897      +/-   ##
==========================================
+ Coverage   73.68%   73.70%   +0.02%     
==========================================
  Files         438      438              
  Lines       26649    26656       +7     
  Branches     3939     3943       +4     
==========================================
+ Hits        19635    19648      +13     
+ Misses       5141     5136       -5     
+ Partials     1873     1872       -1     

see 7 files with indirect coverage changes

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