[TASK] Consistenly update to 2.8.x branch of Symfony packages

To ensure PHP 5.5.0 compatibility as stated in our version constraints,
we limit updating package dependencies within our shipped code
to this PHP version.

Additionally we update these packages to their latest version

Composer commands used:

composer up symfony/console symfony/finder
composer req symfony/debug:^2.7
composer req --dev symfony/stopwatch:^2.8 symfony/process:^2.8 \
  symfony/options-resolver:^2.8 symfony/filesystem:^2.8 \
  symfony/event-dispatcher:^2.8 symfony/yaml:^2.8
composer config platform.php 5.5
composer up --lock

Releases: 7.6
Resolves: #83223
Change-Id: Idb271d632bf472705a3e887c1405fcffb282cb05
Reviewed-on: https://review.typo3.org/54932


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>