Allow creating content security policies by fetching them from remote source

[azasypkin]

Summary

User should be able to create a policy by providing a remote URL where the policy should be fetched from:

1. User goes to https://secutils.dev/ws/web_security__csp__policies
2. Clicks on Fetch policy
3. Once the policy is fetched, user should be able to set the name and saved the policy

[azasypkin]

Handled in 2db6c0a and secutils-dev/secutils-webui@de60ab7