Provide alternative methods to ignore missing parameters when Allow User Variables=False.

[fuine6]

Is your feature request related to a problem? Please describe.
When Allow User Variables=False, MySql.Data can use @` to ignore missing variables.

For example

var connectionString = "Server=127.0.0.1;User ID=root;Password=123456;Database=test;Allow User Variables=False";

using var connection = new MySql.Data.MySqlClient.MySqlConnection(connectionString);

var sql = @"SELECT 1 INTO @`a`; SELECT @`a`;";

try
{
	int a = await connection.QuerySingleOrDefaultAsync<int>(sql);
	Console.WriteLine($"a: {a}");
}
catch (Exception ex)
{
	Console.WriteLine(ex.Message);
}

Output:

a: 1

Describe the solution you'd like
Do this in a similar way.

Additional context
I like to use Allow User Variables=False to avoid typos, but I need a way to use variables in special cases.

[bgrainger]

I didn't know (till now) that MySql.Data had this "back door". It's a clever hack, but I need to consider the backwards-compatibility issues with adopting it into MySqlConnector now: quoting parameters with ` or ' has been legal since 1.0 and it could introduce silent failures to let those be passed through as literals to the MySQL server (instead of being caught in client-side code).