add dart server to package testing (FF-4065)

[leoromanovsky]

No description provided.

[leoromanovsky]

not valid yaml format

[Invalid workflow file: .github/workflows/test-sdk-packages.yml#L50](https://github.com/Eppo-exp/sdk-test-data/actions/runs/13536314793/workflow)
The workflow is not valid. .github/workflows/test-sdk-packages.yml (Line: 50, Col: 15): A sequence was not expected

[leoromanovsky]

I'm getting my head around what's needed here but I think I overlooked something: I thought I could compile from source but looks like some mac os signing might be needed. I'll continue exploration here as this is the hypothetically easiest way to integrate into package testing:

warning: `eppo_dart` (lib) generated 4 warnings (run `cargo fix --lib -p eppo_dart` to apply 1 suggestion)
    Finished `release` profile [optimized] target(s) in 39.78s
INFO: 2025-02-26 11:45:08.366496: Starting server with API server: http://localhost:5000/api
INFO: 2025-02-26 11:45:08.373496: Found native library at: /Users/leo/src/sdk-test-data/package-testing/dart-sdk-relay/lib/native/libeppo_client.dylib
INFO: 2025-02-26 11:45:08.373556: Setting RUST_LIBRARY_PATH to: /Users/leo/src/sdk-test-data/package-testing/dart-sdk-relay/lib/native/libeppo_client.dylib
SEVERE: 2025-02-26 11:45:08.373718: Error setting up native library path: Unsupported operation: Cannot modify unmodifiable map
INFO: 2025-02-26 11:45:08.373914: Initializing Eppo client with API server: http://localhost:5000/api
Unhandled exception:
Invalid argument(s): Failed to load dynamic library 'eppo_dart.framework/eppo_dart': dlopen(eppo_dart.framework/eppo_dart, 0x0001): tried: 'eppo_dart.framework/eppo_dart' (no such file), '/System/Volumes/Preboot/Cryptexes/OSeppo_dart.framework/eppo_dart' (no such file), '/opt/homebrew/Caskroom/flutter/3.27.1/flutter/bin/cache/dart-sdk/bin/./eppo_dart.framework/eppo_dart' (no such file), '/opt/homebrew/Caskroom/flutter/3.27.1/flutter/bin/cache/dart-sdk/bin/../../../eppo_dart.framework/eppo_dart' (no such file), '/opt/homebrew/Caskroom/flutter/3.27.1/flutter/bin/cache/dart-sdk/bin/Frameworks/eppo_dart.framework/eppo_dart' (no such file), '/opt/homebrew/Caskroom/flutter/3.27.1/flutter/bin/cache/dart-sdk/bin/./eppo_dart.framework/eppo_dart' (no such file), '/opt/homebrew/Caskroom/flutter/3.27.1/flutter/bin/cache/dart-sdk/bin/../../../eppo_dart.framework/eppo_dart' (no such file), '/opt/homebrew/Caskroom/flutter/3.27.1/flutter/bin/cache/dart-sdk/bin/Frameworks/eppo_dart.framework/eppo_dart' (no such file), '/usr/lib/eppo_dart.framework/eppo_dart' (no such file, not in dyld cache), 'eppo_dart.framework/eppo_dart' (no such file), '/System/Library/Frameworks/eppo_dart.framework/eppo_dart' (no such file, not in dyld cache)
#0      _open (dart:ffi-patch/ffi_dynamic_library_patch.dart:11:43)
#1      new DynamicLibrary.open (dart:ffi-patch/ffi_dynamic_library_patch.dart:22:12)
#2      new ExternalLibrary.open (package:flutter_rust_bridge/src/platform_types/_io.dart:42:47)
#3      loadExternalLibraryRaw.<anonymous closure>.<anonymous closure> (package:flutter_rust_bridge/src/loader/_io.dart:72:29)
#4      _tryOpen (package:flutter_rust_bridge/src/loader/_io.dart:93:20)
#5      loadExternalLibraryRaw.<anonymous closure> (package:flutter_rust_bridge/src/loader/_io.dart:68:22)
#6      loadExternalLibraryRaw.tryAssumingNonPackaged (package:flutter_rust_bridge/src/loader/_io.dart:49:22)
#7      loadExternalLibraryRaw (package:flutter_rust_bridge/src/loader/_io.dart:66:12)
#8      loadExternalLibrary (package:flutter_rust_bridge/src/loader/_io.dart:14:10)
#9      BaseEntrypoint._loadDefaultExternalLibrary (package:flutter_rust_bridge/src/main_components/entrypoint.dart:141:13)
#10     BaseEntrypoint.initImpl (package:flutter_rust_bridge/src/main_components/entrypoint.dart:48:31)
#11     RustLib.init (package:eppo_sdk/src/rust/frb_generated.dart:29:20)
#12     globalInit (package:eppo_sdk/src/client.dart:14:39)
#13     new EppoClient (package:eppo_sdk/src/client.dart:46:25)
#14     initEppoClient (file:///Users/leo/src/sdk-test-data/package-testing/dart-sdk-relay/bin/server.dart:142:18)
#15     main (file:///Users/leo/src/sdk-test-data/package-testing/dart-sdk-relay/bin/server.dart:72:13)
#16     _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:295:33)
#17     _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

cc @felipecsl @rasendubi