Fix/work package index performance

Dynamically includes the columns required for the fields in the response to various experimental work packages actions to be eager loaded.

This removes some n+1 queries, those when custom fields are involved in particular. In addition, it also does no longer load data that is not used later on.

https://community.openproject.org/work_packages/17550

* [x] version cf broken on wp index #2276
I guess we want to use the current RSpec syntax here (?):
```Ruby
allow(dwp1).to receive(:custom_values).and_return [custom_value]
```
See also line 76 and 78.