[HttpKernel] removed the need to use reflection to get a bundle namespace
[HttpKernel] removed a circular reference that prevents PHP GC to do its job
merged branch fabpot/bundle-leaks (PR #8947)

This PR was merged into the master branch.

Discussion
----------

[HttpKernel] fixes some memory leaks

| Q             | A
| ------------- | ---
| Bug fix?      | kinda
| New feature?  | no
| BC breaks?    | kinda as the Bundle `$reflected` property was removed
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

6307f41 [HttpKernel] removed a circular reference that prevents PHP GC to do its job
49fe3c7 [HttpKernel] removed the need to use reflection to get a bundle namespace