chore: upgrade to v4 of the core SDK

[typotter]

Eppo Internal:

🎟️ Fixes related to v4.0.0 SDK migration
📜 Design Doc: N/A

Motivation and Context

The Android SDK needs to be upgraded to use sdk-common-jvm:4.0.0-SNAPSHOT, which includes breaking changes to the BaseEppoClient constructor signature and requires the format field in configuration JSON. Without this upgrade, the Android SDK cannot use the latest core library.

Description

This PR migrates the Android SDK to be compatible with sdk-common-jvm:4.0.0-SNAPSHOT. The migration addresses two key changes:

1. BaseEppoClient Constructor Signature Change (EppoClient.java:52)

The v4.0.0-SNAPSHOT constructor removed the deprecated host parameter:

• Before (v3): apiKey, sdkName, sdkVersion, host, apiBaseUrl, ...
• After (v4): apiKey, sdkName, sdkVersion, apiBaseUrl, ...

Solution: Use fallback logic apiBaseUrl != null ? apiBaseUrl : host to maintain backward compatibility with code using the deprecated .host() builder method.

2. Configuration Format Field Requirement (EppoClientTest.java:712)

v4.0.0 requires a format field in configuration JSON:

• "format": "CLIENT" for obfuscated/hashed flag keys
• "format": "SERVER" for plain/unobfuscated keys

Solution: Added "format": "CLIENT" to the pre-seeded cache test data in testDifferentCacheFilesPerKey().

How has this been documented?

Code Comments:

• The constructor fallback logic is self-documenting
• Test data format field matches production configuration format

No external documentation changes required as these are internal implementation changes that maintain API compatibility. The public SDK API remains unchanged.

How has this been tested?

Unit Tests: ✅ All passing (100%)

./gradlew test
BUILD SUCCESSFUL

Integration Tests: ✅ All 23/23 passing (100%)

./gradlew eppo:connectedCheck
BUILD SUCCESSFUL
Starting 23 tests on Medium_Phone_API_36.0(AVD) - 16
Medium_Phone_API_36.0(AVD) - 16 Tests 23/23 completed. (0 skipped) (0 failed)

Test Coverage Includes:

1. ✅ Client initialization with deprecated .host() method (backward compatibility)
2. ✅ Client initialization with .apiBaseUrl() method
3. ✅ Offline mode with pre-seeded cache
4. ✅ Multiple API keys with different cache files (testDifferentCacheFilesPerKey)
5. ✅ Configuration change listeners
6. ✅ Assignment evaluation for all variation types (boolean, numeric, string, JSON)

All existing functionality works correctly with the new v4.0.0-SNAPSHOT core library.

[typotter]

getTypedAssignment was protected level and only used by the test suite in the android sdk to test graceful degredation. graceful mode is fully tested (and implemented) in the common sdk, so these tests are redundant.