[HttpFoundation] MongoDbSessionHandler supports auto expiry via configurable expiry_field
feature #11510 [HttpFoundation] MongoDbSessionHandler supports auto expiry via configurable expiry_field (catchamonkey)

This PR was squashed before being merged into the 2.3 branch (closes #11510).

Discussion
----------

[HttpFoundation] MongoDbSessionHandler supports auto expiry via configurable expiry_field

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11508
| License       | MIT
| Doc PR        | no

ToDo

 * [x] Fix Tests

Looking for feedback on this early PR.

This adds a config option that disables the PHP GC method call from doing anything,
It also means that the write method sets up the auto expiring index.

Ref: #11508

Commits
-------

b56b740 [HttpFoundation] MongoDbSessionHandler supports auto expiry via configurable expiry_field