Deprecated passing of `start` value to `find_in_batches` and `find_each` in favour of `begin_at` value.

that complements the `start`parameter to specify where to stop batch processing

- Changed `IN` to `ON` in all note sentences in guides.

Added the SQL equivalent of the find_by method

Update active_record_querying.md

Update active_record_querying.md

Commit 65a2977c added a `pre-wrap` style for white spaces on `.note`
paragraphs. However, this is first inconsistent as other notes like
warnings don't have this style applied. Furthermore, it seems to be
unneeded for mobile devices.

Also revert changes made in #18147 since they aren't needed anymore.

Cross-refs #18138.

[ci skip]

References #18148.

References #18138

Reference: https://github.com/rails/rails/commit/d4fd0bd17709735ac91e434c94fe99429f078c6e

cc @schneems

Reference: https://github.com/rails/rails/commit/f7e4362011ceb1317fd401125d48d7ccb9a1079c

This reverts commit 0f6b101e.

Reason: It's better to let `unscope` be documented. We can add a
separate section for `except`.

The example showed is `except`, however the method "documented" is `unstop`. Fix to align the docs to the example.

Also use appropriate mailer syntax in the `find_each` block.

Put all options for overloading `find` in one section

Add docs on what happens when a numerical argument is provided to last.

Since `last!` behaves exactly the same way but can raise an argument we can consolidate it in the `last` section.

Add docs on what happens when a numerical argument is provided to take.

Since `take!` behaves exactly the same way but can raise an argument we can consolidate it in the `take` section.

Since `find_by!` behaves exactly the same way but can raise an argument we can consolidate it in the `find_by` section.

Add docs for `first` when provided a numerical argument. 

Since `first!` behaves exactly the same way but can raise an argument we can consolidate it in the `first` section.

Closes #15541.

duplicating API reference in guides. Also ✂ [ci skip]

[ci skip]