Add feature filter types for users

What does this MR do?

Remembers "feature enabled or not" choice for each user in a feature_filter field to in user preferences for gitlab.com

Background:

• The MR to add !21658 (merged) a security feature to 10% of users doesn't work properly
• Chatops percentage rollout uses Flipper gem "Percentage of the time" rollout but doesn't remember the choice for each user every time.
• that Actor based user percentage rollout doesn't scale properly as it keeps all user IDs in one text field in feature_gates table

# actor based approach does not scale as it keeps the User ids in a string field.
 Feature.enable(:discover_security, current_user)
  3 | discover_security | actors             | User:1  | 2020-02-09 13:06:04.699212 | 2020-02-09 13:06:04.699212
  4 | discover_security | actors             | User:66 | 2020-02-09 13:06:15.43271  | 2020-02-09 13:06:15.43271

• Cookie based approaches do not remember the choice across browsers and devices.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team