Add authentication information to usage ping

What does this MR do?

Related to #213931 (closed)

Currently, we only track LDAP in the self-managed feedback we receive back in usage ping. For us to be able to better understand which authentication strategies we should invest in, we should get some basic information on what instances tend to use.

This adds authentication info In the manage stage section of usage ping. Additions include which omniauth providers are enabled, and whether group SAML is in use.

Example:

   :manage=>
    {:events=>28,
     :groups=>21,
     :ldap_keys=>0,
     :ldap_users=>1,
     :users_created=>57,
     :value_stream_management_customized_group_stages=>0,
     :projects_with_compliance_framework=>0,
# NEW ATTRIBUTES BELOW
     :ldap_servers=>2,
     :ldap_group_sync_enabled=>true,
     :ldap_admin_sync_enabled=>false,
     :omniauth_providers=>["google_oauth2"],
     :group_saml_enabled=>true},

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