Describe the bug
When configuring the DbContext to use "utf8mb4" as the character set and "utf8mb4_unicode_ci" as the collation, the first migration generated in an EF Core project does not include the specified collation. As a result, the created database uses an unexpected collation.

Configuration in DbContext:

            builder.UseCollation("utf8mb4_unicode_ci");
            builder.HasCharSet("utf8mb4", DelegationModes.ApplyToDatabases);

Generated Migration

            migrationBuilder.AlterDatabase()
                .Annotation("MySql:CharSet", "utf8mb4");

I was expecting the following:

            migrationBuilder.AlterDatabase(
                collation: "utf8mb4_unicode_ci")
                .Annotation("MySql:CharSet", "utf8mb4");

Is this behaviour expected?

To Reproduce

1. Add following configuration to DbContext: (OnModelCreating)

            builder.UseCollation("utf8mb4_unicode_ci");
            builder.HasCharSet("utf8mb4", DelegationModes.ApplyToDatabases);

2. Create a new EF Core project without migrations.
3. Add the first migration.
   The generated migration does not include the configured collation.

Expected behavior
When a collation is explicitly configured, it should be included in the generated migration.

Technical details (please complete the following information):

• Database server version: [MariaDB 11.4.9]
• Operating system: [Windows 11]
• Pomelo.EntityFrameworkCore.MySql version: [9.0.0.efcore.9.0.0]
• Other technical details: [ASP.NET Core]