[RFC]: Support for PSR-6 & PSR-16 v3

[boesing]

Feature Request

Q	A
New Feature	yes
BC Break	no

Summary

PSR-6 and PSR-16 has v2 & v3 available. Since I dont see the point of supporting v2 AND v3, we should be fine with supporting v1 and v3. We could use composer/deprecated-package-versions along with an autoload check for the psr/cache version to use class_alias to provide support for both v1 & v3 of psr/cache and psr/simple-cache.

Same compatibility layer is used in laminas/laminas-cli to support both symfony/console v4 & v5.

We could also use composer-runtime-api requirement but I am not yet fully convinced that anyone is able to use composer in v2 but I am open for this change, if the majority is fine with having a hard requirement to the composer-runtime-api.