Fix obsolete Testcontainers API calls after 4.10.0 upgrade

[Copilot]

Testcontainers 4.10.0 deprecated parameterless constructors in favor of constructors that accept the image name directly.

Changes

• FirebirdSchemaIntegrationTests: Updated FirebirdSqlBuilder initialization to pass image to constructor
• SnowflakeSchemaIntegrationTests: Updated ContainerBuilder initialization to pass image to constructor

- var container = new FirebirdSqlBuilder()
-     .WithImage("jacobalberty/firebird:v4.0")
+ var container = new FirebirdSqlBuilder("jacobalberty/firebird:v4.0")
      .Build();

The .WithImage() fluent method is replaced by constructor parameter as required by the new API.

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