Provide dynamic file stream wrapper validation on config form validation

Problem/Motivation

When we are using external file system modules like s3fs, we need to deliver hotjar js files via s3 buckets.
For this, we should be able to configure s3:// stream wrapper on the configuration form

Steps to reproduce

Goto configuration form
Provide "s3://hotjar/hotjar.script.js" in "Hotjar snippet path" field
Submit the form.
Though s3 file stream wrapper is valid, we are just validating for public and private stream wrappers

Proposed resolution

Add validation.
Patch is attached.

Remaining tasks

User interface changes

API changes

Data model changes