Make XResource.get() more ergonomic over missing options

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Issue details

For example, for a com.pulumi.aws.ec2.SecurityGroup the get method has the following signature:

    /**
     * Get an existing Host resource's state with the given name, ID, and optional extra
     * properties used to qualify the lookup.
     *
     * @param name The _unique_ name of the resulting resource.
     * @param id The _unique_ provider ID of the resource to lookup.
     * @param state
     * @param options Optional settings to control the behavior of the CustomResource.
     */
    public static SecurityGroup get(String name, Output<String> id, @Nullable SecurityGroupState state, @Nullable com.pulumi.resources.CustomResourceOptions options) {
        return new SecurityGroup(name, id, state, options);
    }

Note how String id is not auto-promoted to Output<String> and state, options must be supplied as nulls and cannot be omitted. This is a minor ergonomics problem but perhaps we can enhance the API here to read better.

Affected area/feature

Start with the XResource.get API and the SecurityGroup.get signature shown in the issue. Compare how generated get methods handle String IDs, state, and options, then define a consistent ergonomic API and its compatibility requirements. Done means the design is agreed and the relevant generated APIs and tests cover omitted optional values.