CreateTable docs should tell what happens if the table already exists

The docs should be explicit about what happens if the table already exists in the schema. Will an exception be thrown? Will it be a no-op? Will it truncate & overwrite the existing table?
In general, this would be useful info for man of the `MigrationBuilder` methods.

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#### Document Details

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* ID: 187896bd-0e67-923b-9863-d50ba411b9c0
* Version Independent ID: efc25ab0-39bd-2bcc-cd56-61fb75608048
* Content: [MigrationBuilder.CreateTable Method (Microsoft.EntityFrameworkCore.Migrations)](https://docs.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.migrations.migrationbuilder.createtable?view=efcore-5.0)
* Content Source: [dotnet/xml/Microsoft.EntityFrameworkCore.Migrations/MigrationBuilder.xml](https://github.com/dotnet/EntityFramework.ApiDocs/blob/live/dotnet/xml/Microsoft.EntityFrameworkCore.Migrations/MigrationBuilder.xml)
* Product: **ef-core-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **avickers**