Rely on `symfony/deprecation-contracts` for deprecations

[alexislefebvre]

Is your feature request related to a problem? Please describe.
Current deprecations use a code like this:

LiipFunctionalTestBundle/src/Test/WebTestCase.php

Line 282 in 8c91766

@trigger_error('Setting "environment" property is deprecated, please use static::$env.', \E_USER_DEPRECATED);

Describe the solution you'd like

• https://github.com/symfony/deprecation-contracts could be used instead.

• Consider adding more deprecations if Symfony has built-in helpers that replace the ones from this bundle:

  • if it requires a minimal version that is higher than the minimal version required by this bundle
    • then throw a deprecation only if this version constraint is fulfilled by the project

Describe alternatives you've considered
.

Additional context
.