[Symfony 6] Drop support for services as container parameters

Problem/Motivation

Over in #3161889: [META] Symfony 6 compatibility we have discovered that Symfony has tightened up the definition of a value in a ParameterBag:

public function set(string $name, array|bool|string|int|float|null $value) {
  $this->parameters[$name] = $value;
}

ie. the value cannot be an object.

The only place we rely on this in core is a single test case that checks that our container dumper correctly stores service references as container parameters:

        [
          ['reference' => new Reference('referenced_service')],
          ['reference' => $this->getServiceCall('referenced_service')],
          TRUE,
        ],

getServiceCall() returns an object, which can no longer be stored in a Symfony 6 ParameterBag.

Symfony's PHP dumper does not support service references as parameters; https://github.com/symfony/dependency-injection/blob/6c566c7b29e36daa806...

Steps to reproduce

Proposed resolution

Drop support for service references as parameters.

Remaining tasks

Decide if we need a deprecation notice for this.
Decide whether to throw an explicit exception or just let it fail.

User interface changes

API changes

Data model changes

Release notes snippet