Introduce fluent methods for CustomTool

[dmason30]

Refactors the CustomTool to:

CustomTool::make(
    name: 'custom_tool',
    description: 'This is a custom tool',
)
    ->withStringParameter(name: 'name', description: 'The name of the user', required: true)
    ->withIntegerParameter(name: 'age', description: 'The age of the user')
    ->using(function (string $name, ?int $age = null) {
        return sprintf('Hello, %s! You are %d years old.', $name, $age ?? 'unknown');
    }),
);