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/include/check_key_reads.inc

@@ -2,5 +2,5 @@
 let $key_reads= query_get_value(SHOW STATUS LIKE 'key_reads',Value,1);
 --disable_query_log
 eval SELECT IF($key_reads = 0, "Yes!", "No!") as 'Zero key reads?';
-FLUSH STATUS;
+FLUSH GLOBAL STATUS;
 --enable_query_log

mysql-test/include/query_cache.inc

@@ -31,7 +31,7 @@ set GLOBAL query_cache_size = 1355776;
 #
 # Without auto_commit.
 #
-flush status;
+flush global status;
 set autocommit=0;
 eval create table t1 (a int not null)$partitions_a;
 insert into t1 values (1),(2),(3);
@@ -129,7 +129,7 @@ connection default;
 SHOW VARIABLES LIKE 'have_query_cache';
 
 SET GLOBAL query_cache_size = 204800;
-flush status;
+flush global status;
 SET @@autocommit=1;
 eval SET SESSION DEFAULT_STORAGE_ENGINE = $engine_type;
 eval CREATE TABLE t2 (s1 int, s2 varchar(1000), key(s1))$partitions_s1;

mysql-test/include/query_cache_partitions.inc

@@ -40,7 +40,7 @@ show create table t1;
 
 INSERT INTO t1 VALUES (1, now(), 0);
 
-flush status;
+flush global status;
 show status like "Qcache_queries_in_cache";
 show status like "Qcache_hits";
 
@@ -76,7 +76,7 @@ show create table t1;
 
 INSERT INTO t1 VALUES (1, now(), 0);
 
-flush status;
+flush global status;
 show status like "Qcache_queries_in_cache";
 show status like "Qcache_hits";
 
@@ -97,7 +97,7 @@ drop table t1;
 --echo #
 
 flush query cache;
-flush status;
+flush global status;
 
 SET GLOBAL query_cache_size=1024*1024*512;
   CREATE TABLE `t1` (

mysql-test/include/query_cache_sql_prepare.inc

@@ -30,7 +30,7 @@ connection default;
 
 set @initial_query_cache_size = @@global.query_cache_size;
 set @@global.query_cache_size=102400;
-flush status;
+flush global status;
 --disable_warnings
 drop table if exists t1;
 --enable_warnings
@@ -485,7 +485,7 @@ drop table if exists t1;
 --enable_warnings
 create table t1 (a varchar(255));
 insert into t1 (a) values ("Pack my box with five dozen liquor jugs.");
-flush status;
+flush global status;
 prepare stmt from "select a from t1";
 execute stmt;
 set @@global.query_cache_size=0;