User Availability - Allow users to schedule un-setting of their status

What does this MR do?

This MR adds a clear status dropdown to the set user status modal.

Screenshots (strongly suggested)

Before Form Open dropdown Date set
Screenshot_2021-03-15_at_16.03.40 Screenshot_2021-03-16_at_16.38.41 Screenshot_2021-03-16_at_16.38.51 Screenshot_2021-03-16_at_16.39.49

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

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

Related to #262086 (closed)

Edited by Brandon Labuschagne