[Icons] use dedicated cache pool

[IndraGunawan]

Q	A
Bug fix?	no
New feature?	no
Issues	Fix #...
License	MIT

based on @stof comment on EasyAdminBundle repository EasyCorp/EasyAdminBundle#6507 (comment)

you should probably create a dedicated cache pool inheriting its configuration from cache.system instead of using cache.system directly. this is how core Symfony components work (allowing them to avoid having to care about conflicting keys between the caches of different component, as the key only needs to be unique inside the cache pool)

[Kocal]

Thank you @IndraGunawan.