[views] simplify and fix the TreeView (closes #16055814) Simplify the (internal) TreeView._init_params() method to get rid of the useless 'initial_thru_ajax' argument. The ajax tree view was not working properly when loaded via ajax, for instance from a lazy tab. This was due to the buggy protection against double javascript/ css inclusion, which is no more needed server-side as it is now implemented client-side. Deprecate use of the initial_thru_ajax argument of the TreeView.call() method.

### Requirements for tests in various cubicweb/**/test directories. ###

## shared by several test folders
cubicweb-card
docutils
Twisted < 16.0.0
webtest

## cubicweb/test
Pygments
mock
#fyzz XXX pip install fails
cubicweb-file
cubicweb-localperms
cubicweb-tag

## cubicweb/devtools/test
flake8

## cubicweb/hooks/test
psycopg2

## cubicweb/pyramid/test
pyramid >= 1.5.0
waitress >= 0.8.9
wsgicors >= 0.3
pyramid_multiauth

## cubicweb/sobject/test
cubicweb-comment