MDEV-33145 Add FLUSH GLOBAL STATUS

- FLUSH GLOBAL STATUS now resets most global_status_vars.
  At this stage, this is mainly to be used for testing.
- FLUSH SESSION STATUS added as an alias for FLUSH STATUS.
- FLUSH STATUS does not require any privilege (before required RELOAD).
- FLUSH GLOBAL STATUS requires RELOAD privilege.
- All global status reset moved to FLUSH GLOBAL STATUS.
- Replication semisync status variables are now reset by
  FLUSH GLOBAL STATUS.
- In test cases, the only changes are:
  - Replace FLUSH STATUS with FLUSH GLOBAL STATUS
  - Replace FLUSH STATUS with FLUSH STATUS; FLUSH GLOBAL STATUS.
    This was only done in a few tests where the test was using SHOW STATUS
    for both local and global variables.
- Uptime_since_flush_status is now always provided, independent if
  ENABLED_PROFILING is enabled when compiling MariaDB.
- @@global.Uptime_since_flush_status is reset on FLUSH GLOBAL STATUS
  and @@session.Uptime_since_flush_status is reset on FLUSH SESSION STATUS.
- When connected, @@session.Uptime_since_flush_status is set to 0.

mysql-test/main/flush_notembedded.test

@@ -65,3 +65,21 @@ DROP VIEW v0, v1, v2;
 --echo #
 --echo # End of 10.6 tests
 --echo #
+
+--echo #
+--echo # MDEV-33145 Add FLUSH GLOBAL STATUS
+--echo #
+
+CREATE USER mysqltest@localhost;
+GRANT USAGE ON *.* TO mysqltest@localhost;
+
+connect(con1, localhost, mysqltest);
+FLUSH STATUS;
+FLUSH SESSION STATUS;
+--error ER_SPECIFIC_ACCESS_DENIED_ERROR
+FLUSH GLOBAL STATUS;
+disconnect con1;
+connection default;
+DROP USER mysqltest@localhost;
+
+--echo # End of 11.5 tests