Extend documentation about Form validation with examples

[cnotv]

Description

Given the episode with https://github.com/rancher/dashboard/issues/6816, it has been complex to catch the right configuration for each case. We want then to list all the possible way to use the form validation, the procedure to extend existing cases and examples for each of them, based on past experiences.

Example cases, but not all:

• Use of Global validation rules
• Use of Custom validation rules (e.g. #6633)
• Creation and use of Validation factory rules (e.g. #6633)
• View abstraction for global validation through configuration (e.g. #6633)
• View abstraction for custom validation through configuration (e.g. #6633)
• Validation of k8s Resource type with CRU component
• Validation of non-k8s Resource type with CRU component (e.g. #6633)
• Validation of inputs without form
• Validation using templates and <component> (e.g. #7657)

[gaktive]

We need to re-evaluate how we do form validation since there may be a library we could leverage.