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/query_cache_with_views.result

@@ -5,7 +5,7 @@ set @save_query_cache_type=@@global.query_cache_type;
 set GLOBAL query_cache_type=ON;
 set LOCAL query_cache_type=ON;
 set GLOBAL query_cache_size=1355776;
-flush status;
+flush global status;
 create table t1 (a int, b int);
 create view v1 (c,d) as select sql_no_cache a,b from t1;
 create view v2 (c,d) as select a+rand(),b from t1;
@@ -46,7 +46,7 @@ Variable_name	Value
 Qcache_hits	0
 drop view v1,v2;
 set query_cache_type=demand;
-flush status;
+flush global status;
 create view v1 (c,d) as select sql_cache a,b from t1;
 show status like "Qcache_queries_in_cache";
 Variable_name	Value
@@ -136,7 +136,7 @@ unlock tables;
 set query_cache_wlock_invalidate=default;
 drop view v1;
 drop table t1;
-flush status;
+flush global status;
 create table t1 (a int, b int);
 create algorithm=temptable view v1 as select * from t1;
 select * from v1;