This reverts commit b67d5c6dedbf033515a96a95d24d085bf99a0d07, reversing
changes made to 2e018361c7c51e36d1d98bf770b7456d78dee68b.
Reason: #35186 may cause that silently leaking information when people
upgrade the app.
We need deprecation first before making this.
`relation.create` populates scope attributes to new record by `scoping`,
it is necessary to assign the scope attributes to the record and to find
STI subclass from the scope attributes.
But the effect of `scoping` is class global, it was caused undesired
behavior that pollute all class level querying methods in initialization
block and callbacks (`after_initialize`, `before_validation`,
`before_save`, etc), which are user provided code.
To avoid the leaking scope issue, restore the original current scope
before initialization block and callbacks are invoked.
Fixes#9894.
Fixes#17577.
Closes#31526.
Before this commit, returning `false` in an ActiveRecord `before_` callback
such as `before_create` would halt the callback chain.
After this commit, the behavior is deprecated: will still work until
the next release of Rails but will also display a deprecation warning.
The preferred way to halt a callback chain is to explicitly `throw(:abort)`.
