[4.0] Session Save Path error

[joomdonation]

Steps to reproduce the issue

1. Install Joomla 4

2. Access to Global Configuration area, look at System tab, In Session Handler, choose Filesystem, Session Save Path setting will be displayed. Two problems here:

• I am using windows and when I enter a valid path like D:\www\sessiondata, it is not being saved. Look like a problem with path filter
• I entered a wrong path like home/abc. The system should validate and makes sure the path is valid before saving. However, it saves the wrong path anyway and makes the application completely broken (see the screenshot below)

[mbabker]

Addressed via #19431