RANGER-5627: Support configuration-based super users and super groups in Ranger Admin

[ramackri]

What changes were proposed in this pull request?

Implements RANGER-5627: configuration-based
Ranger Admin super users and super groups via ranger.admin.super.users and
ranger.admin.super.groups in ranger-admin-site.xml.

Problem addressed: Externally authenticated users (LDAP/Kerberos/OIDC/SAML) could
not be designated as Ranger administrators without Ranger managed DB roles. Deployments
relied on shared local admin accounts, limiting enterprise IdM integration, SSO/K8s
models, and per-user auditability.

Solution: Matching users receive full admin session flags, Spring Security roles,
module permissions, and REST authorization at login without changing
x_portal_user_role. Authentication provider remains independent of the elevation
decision. Backward compatible when both config properties are empty. Re-login
required after config or UserSync group membership changes.

How was this patch tested?

1. Unit tests

Run from repo root:

mvn test -pl security-admin \
  -Dtest=TestRangerSuperUserConfig,TestSessionMgr,TestUserMgr,TestXUserMgr,TestRangerBizUtil,TestRoleDBStore \
  -Dfrontend.skip=true

Result: All targeted unit tests pass.

Test class	Coverage
TestRangerSuperUserConfig	Config parsing, enable/disable, user/group match
TestSessionMgr	Session flags and module permissions at login
TestUserMgr	Authentication roles and profile overrides
TestXUserMgr	getSyncedGroupsForUser vs getGroupsForUser
TestRangerBizUtil	isUserRangerAdmin, access checks
TestRoleDBStore	Role list bypass for elevated sessions

For more details:
#1000