Update integration tests to use host.testcontainers.internal

[minwoox]

Motivation
While I was running the integration test, I found out that host.docker.internal doesn't work correctly on Linux. (It worked on Mac and Windows.) host.docker.internal is used for the container to access the host but the DNS resolution was keeping failing. While I was debugging on it, I also found out that the Testcontainers provides host.testcontainers.internal for the same purpose and there's no reason not to use it. https://java.testcontainers.org/features/networking/

Modification

• Use host.testcontainers.internal instead of host.docker.internal

Result

• The integration tests now run successfully on Linux.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.16%. Comparing base (95048ae) to head (40ddc19).
⚠️ Report is 96 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #303 +/- ##
=========================================
Coverage 86.16% 86.16% Complexity 361 361 =========================================
Files 42 42 Lines 1178 1178 Branches 97 97 =========================================
Hits 1015 1015 Misses 116 116 Partials 47 47 

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