Deprecations

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12625, #12605, #12628, #12622, #12642, #12609, #12651, #12604
| License       | MIT
| Doc PR        | -

Cherry-picking some pending PRs to make them move forward
I should benchmark with https://blackfire.io/ :)
As this is executed only once, I'm not sure this is relevant.
Is there any better way?