[Symfony 6] Add return types to Symfony Console application methods

Problem/Motivation

In Symfony 6, return types have been added to methods in Symfony\Component\Console\Application:

  protected function getCommandName(InputInterface $input): ?string {

  protected function getDefaultCommands(): array {

  public function getDefinition(): InputDefinition {

We need to add these for our applications to work on Symfony 6.

Steps to reproduce

Proposed resolution

Add the return types.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet