add support for Symfony 8

[dmaicher]

Still quite a few deps on 7.4 due to other dependencies

$ composer show symfony/*
symfony/browser-kit                8.0.x-dev 33746d8 Simulates the behavior of a web browser, allowing you to make requests, click on links and submit forms programmatically
symfony/cache                      7.4.x-dev 5005632 Provides extended PSR-6, PSR-16 (and tags) implementations
symfony/cache-contracts            dev-main 5d68a57  Generic abstractions related to caching
symfony/clock                      8.0.x-dev be52243 Decouples applications from the system clock
symfony/config                     7.4.x-dev caa1de3 Helps you find, load, combine, autofill and validate configuration values of any kind
symfony/console                    7.4.x-dev c3da862 Eases the creation of beautiful and testable command line interfaces
symfony/dependency-injection       7.4.x-dev 287e74a Allows you to standardize and centralize the way objects are constructed in your application
symfony/deprecation-contracts      dev-main 63afe74  A generic function and convention to trigger deprecation notices
symfony/doctrine-bridge            7.4.x-dev e24fcce Provides integration for Doctrine with various Symfony components
symfony/dom-crawler                8.0.x-dev 849ea12 Eases DOM navigation for HTML and XML documents
symfony/error-handler              8.0.x-dev e483666 Provides tools to manage errors and ease debugging PHP code
symfony/event-dispatcher           7.4.x-dev 899a660 Provides tools that allow your application components to communicate with each other by dispatching events and listening to them
symfony/event-dispatcher-contracts dev-main 59eb412  Generic abstractions related to dispatching event
symfony/filesystem                 7.4.x-dev 633c6fd Provides basic utilities for the filesystem
symfony/finder                     7.4.x-dev 38665c9 Finds files and directories via an intuitive fluent interface
symfony/framework-bundle           7.4.x-dev c3fe99c Provides a tight integration between Symfony components and the Symfony full-stack framework
symfony/http-foundation            8.0.x-dev 1afeca4 Defines an object-oriented layer for the HTTP specification
symfony/http-kernel                7.4.x-dev 41b81fa Provides a structured process for converting a Request into a Response
symfony/options-resolver           7.4.x-dev 3324bca Provides an improved replacement for the array_replace PHP function
symfony/password-hasher            8.0.x-dev 80e7c7e Provides password hashing utilities
symfony/polyfill-ctype             1.x-dev a3cc8b0   Symfony polyfill for ctype functions
symfony/polyfill-intl-grapheme     1.x-dev 3808721   Symfony polyfill for intl's grapheme_* functions
symfony/polyfill-intl-normalizer   1.x-dev 3833d72   Symfony polyfill for intl's Normalizer class and related functions
symfony/polyfill-mbstring          1.x-dev 6d857f4   Symfony polyfill for the Mbstring extension
symfony/polyfill-php80             1.x-dev 0cc9dd0   Symfony polyfill backporting some PHP 8.0+ features to lower PHP versions
symfony/polyfill-php81             1.x-dev 4a4cfc2   Symfony polyfill backporting some PHP 8.1+ features to lower PHP versions
symfony/polyfill-php84             1.x-dev 4acd8b3   Symfony polyfill backporting some PHP 8.4+ features to lower PHP versions
symfony/polyfill-php85             1.x-dev 65345af   Symfony polyfill backporting some PHP 8.5+ features to lower PHP versions
symfony/process                    7.4.x-dev 7ca8dc2 Executes commands in sub-processes
symfony/property-access            8.0.x-dev 74df691 Provides functions to read and write from/to an object or array using a simple string notation
symfony/property-info              8.0.x-dev b826ccd Extracts information about PHP class' properties using metadata of popular sources
symfony/routing                    8.0.x-dev 7b07c24 Maps an HTTP request to a set of configuration variables
symfony/security-bundle            8.0.x-dev 8130dd3 Provides a tight integration of the Security component into the Symfony full-stack framework
symfony/security-core              8.0.x-dev e58cae2 Symfony Security Component - Core Library
symfony/security-csrf              8.0.x-dev 8736267 Symfony Security Component - CSRF Library
symfony/security-http              8.0.x-dev 3cd985c Symfony Security Component - HTTP Integration
symfony/service-contracts          dev-main 4511256  Generic abstractions related to writing services
symfony/stopwatch                  7.4.x-dev 8a24af0 Provides a way to profile code
symfony/string                     7.4.x-dev bc78521 Provides an object-oriented API to strings and deals with bytes, UTF-8 code points and grapheme clusters in a unified way
symfony/translation-contracts      dev-main 65a8bc8  Generic abstractions related to translation
symfony/twig-bridge                8.0.x-dev 475090d Provides integration for Twig with various Symfony components
symfony/twig-bundle                8.0.x-dev 4505b86 Provides a tight integration of Twig into the Symfony full-stack framework
symfony/type-info                  8.0.x-dev 3f3a41e Extracts PHP types information.
symfony/var-dumper                 8.0.x-dev d971ae4 Provides mechanisms for walking through any arbitrary PHP variable
symfony/var-exporter               8.0.x-dev 7d3723b Allows exporting any serializable PHP data structure to plain PHP code
symfony/yaml                       7.4.x-dev 0d7c67f Loads and dumps YAML files