feature #16376 [Security] Document the new remember me system (caliendojulien, parijke, wouterj)

This PR was merged into the 5.3 branch.

Discussion
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[Security] Document the new remember me system

Fixes #15721, fixes #16149
Replaces #15464, replaces #15893
Ref #15908

In Symfony 5.3, along with the new authentication system, we also somewhat silently introduced a new remember me system. Time to update the remember me docs with all new features :)

This PR also includes 2 commits from open PRs in this repository. We've been very late with this one, and community members have already invested time in contributing necessary changes to the docs before. They deserve the credits :)

`@javiereguiluz` I'm sorry for not informing you of this work before, I see you just merged a third PR that is replaced by this one.

Commits
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5ac2d26 Document the new remember me system
2df2275 Added the way to activate remember me in the new authentication system
d36b949 Update remember_me.rst

Author: wouterj