[7.x] Add copy_from parameter for set ingest processor (#63540)

[danhermann]

Relates to #55682 and #51046, and refractor the code of #56985.

The main point of this PR is adding a copy_from parameter for set ingest processor to support copy the value of one field to another. We can copy boolean, number, array, object and other data types by the parameter copy_from instead of using template snippet which only produces string value.

Why adding a new parameter to implement the copy function but not modifying the template snippet so that it can produce object or array value ? I think we can make it compatible with older versions, users can still use template snippet to copy the produced string value to other field, but also can use copy_from to copy object or array value from one field to another.

The main changes are:

1. Add copy_from parameter for set ingest processor.
2. Add unit test and yml test for the change.
3. Update the set processor's document.

Backport of #63540

[elasticmachine]

Pinging @elastic/es-core-features (Team:Core/Features)