Add maglnet/composer-require-checker in CI

[Jean85]

Problem Statement

getsentry/sentry-symfony#714 (comment):

Btw, sentry/sentry has the same issue in GuzzleTracingMiddleware.

Solution Brainstorm

@cleptric we should avoid similar issues in the future by adding https://packagist.org/packages/maglnet/composer-require-checker in CI

Originally posted by @Jean85 in getsentry/sentry-symfony#714 (comment)

We can also use https://packagist.org/packages/irstea/composer-require-checker-shim if we don't want to pollute our dependencies.

[Jean85]

Same as getsentry/sentry-symfony#716

[ste93cry]

The GuzzleTracingMiddleware class is not used by this package and it was provided mostly as an example for the tracing feature itself. I don't think we should require a package used by it if the class itself is optional. Besides that, I'm totally favourable to use maglnet/composer-require-checker in general 👍

[cleptric]

There is indeed nothing to be fixed here. The GuzzleTracingMiddleware requires the Guzzle HTTP client to work, so there is no need to construct the URI dynamically.

Adding the require checker might be worth doing.

[cleptric]

With 4.0 I think we're good here.