[Security] fixed issue where x509 authentication clears unrelated tokens

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8226
| License       | MIT
| Doc PR        | symfony/symfony-docs#2741

TODO:
- [x] Feedback on change to make sure security is not affected
- [x] Fix other authentication listeners (they suffer the same problem)
- [x] Write unit tests for bug and maybe a few listener classes as well

This pull request is the summary of the problem mentioned in the ticket above.
It only fixes the "disappearing token" problem for one authentication provider, not all. If acceptable, the change needs to be applied to all authentication listeners since they always clear all tokens from the security context.

Any help or feedback is greatly appreciated.