feature #20735 Deprecate ClassCollectionLoader and Kernel::loadClassCache (dbrumann)
feature #20735 Deprecate ClassCollectionLoader and Kernel::loadClassCache (dbrumann)

This PR was merged into the 3.3-dev branch.

Discussion
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Deprecate ClassCollectionLoader and Kernel::loadClassCache

| Q             | A
| ------------- | ---
| Branch?       | "master"
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #20668
| License       | MIT

As suggested by @nicolas-grekas in #20668 I added deprecation notices to ClassCollectionLoader and Kernel::loadClassCache.

Commits
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660d79a186 Deprecates ClassCache-cache warmer.

symfony/twig-bundle,symfony/twig-bundle