MDEV-23379 Deprecate&ignore InnoDB concurrency throttling parameters

The parameters innodb_thread_concurrency and innodb_commit_concurrency
were useful years ago when both computing resources and the implementation
of some shared data structures were limited. MySQL 5.0 or 5.1 had trouble
scaling beyond 8 concurrent connections. Most of the scalability bottlenecks
have been removed since then, and the transactions per second delivered
by MariaDB Server 10.5 should not dramatically drop upon exceeding the
'optimal' number of connections.

Hence, enabling any concurrency throttling for InnoDB actually makes
things worse. We have seen many customers mistakenly setting this to a
small value like 16 or 64 and then complaining the server was slow.

Ignoring the parameters allows us to remove some normally unused code
and data structures, which could slightly improve performance.

innodb_thread_concurrency, innodb_commit_concurrency,
innodb_replication_delay, innodb_concurrency_tickets,
innodb_thread_sleep_delay, innodb_adaptive_max_sleep_delay:
Deprecate and ignore; hard-wire to 0.

The column INFORMATION_SCHEMA.INNODB_TRX.trx_concurrency_tickets
will always report 0.

Author: dr-m

extra/mariabackup/xtrabackup.cc

@@ -5376,7 +5376,6 @@ static bool xtrabackup_prepare_func(char** argv)
 	xb_filters_init();
 
 	srv_log_group_home_dir = NULL;
-	srv_thread_concurrency = 1;
 
 	if (xtrabackup_incremental) {
 		srv_operation = SRV_OPERATION_RESTORE_DELTA;

mysql-test/include/mix1.inc

@@ -1183,10 +1183,6 @@ set @my_innodb_autoextend_increment=@@global.innodb_autoextend_increment;
 set global innodb_autoextend_increment=8;
 set global innodb_autoextend_increment=@my_innodb_autoextend_increment;
 
-set @my_innodb_commit_concurrency=@@global.innodb_commit_concurrency;
-set global innodb_commit_concurrency=0;
-set global innodb_commit_concurrency=@my_innodb_commit_concurrency;
-
 #
 # Bug #37830: ORDER BY ASC/DESC - no difference
 #

mysql-test/suite/innodb/r/innodb_buffer_pool_resize_debug.result

@@ -1,5 +1,4 @@
 set global innodb_file_per_table=ON;
-set global innodb_thread_concurrency=20;
 connect  con1,localhost,root,,;
 connect  con2,localhost,root,,;
 connect  con3,localhost,root,,;

mysql-test/suite/innodb/r/innodb_bug42101-nonzero.result

@@ -1797,9 +1797,6 @@ DROP TABLE t1;
 set @my_innodb_autoextend_increment=@@global.innodb_autoextend_increment;
 set global innodb_autoextend_increment=8;
 set global innodb_autoextend_increment=@my_innodb_autoextend_increment;
-set @my_innodb_commit_concurrency=@@global.innodb_commit_concurrency;
-set global innodb_commit_concurrency=0;
-set global innodb_commit_concurrency=@my_innodb_commit_concurrency;
 CREATE TABLE t1 (a int, b int, c int, PRIMARY KEY (a), KEY t1_b (b))
 ENGINE=InnoDB;
 INSERT INTO t1 (a,b,c) VALUES (1,1,1), (2,1,1), (3,1,1), (4,1,1);

mysql-test/suite/innodb/r/innodb_bug42101.result

@@ -24,10 +24,6 @@ call mtr.add_suppression("Cannot add field .* in table .* because after adding i
 call mtr.add_suppression("\\[ERROR\\] InnoDB: in ALTER TABLE `test`.`t1`");
 call mtr.add_suppression("\\[ERROR\\] InnoDB: in RENAME TABLE table `test`.`t1`");
 
-SET @innodb_thread_sleep_delay_orig = @@innodb_thread_sleep_delay;
-
-SET @innodb_thread_concurrency_orig = @@innodb_thread_concurrency;
-
 --disable_warnings
 SET @innodb_rows_deleted_orig = (SELECT variable_value FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_rows_deleted');
 SET @innodb_rows_inserted_orig = (SELECT variable_value FROM information_schema.global_status WHERE LOWER(variable_name) = 'innodb_rows_inserted');
@@ -2503,9 +2499,6 @@ DROP TABLE bug35537;
 DISCONNECT c1;
 CONNECTION default;
 
-SET GLOBAL innodb_thread_sleep_delay = @innodb_thread_sleep_delay_orig;
-SET GLOBAL innodb_thread_concurrency = @innodb_thread_concurrency_orig;
-
 -- enable_query_log
 
 # Clean up after the Bug#55284/Bug#58912 test case.

mysql-test/suite/innodb/r/innodb_mysql.result

@@ -9,8 +9,6 @@
 --disable_query_log
 set @old_innodb_buffer_pool_size = @@innodb_buffer_pool_size;
 set @old_innodb_file_per_table = @@innodb_file_per_table;
-set @old_innodb_thread_concurrency = @@innodb_thread_concurrency;
-set @old_innodb_thread_sleep_delay = @@innodb_thread_sleep_delay;
 set @old_innodb_disable_resize = @@innodb_disable_resize_buffer_pool_debug;
 set global innodb_disable_resize_buffer_pool_debug = OFF;
 call mtr.add_suppression("\\[ERROR\\] InnoDB: failed to allocate memory for buffer pool chunk");
@@ -22,7 +20,6 @@ call mtr.add_suppression("\\[ERROR\\] InnoDB: failed to allocate memory for buff
 let $wait_timeout = 180;
 
 set global innodb_file_per_table=ON;
-set global innodb_thread_concurrency=20;
 
 connect (con1,localhost,root,,);
 connect (con2,localhost,root,,);
@@ -178,8 +175,6 @@ drop table t6;
 --disable_query_log
 set global innodb_buffer_pool_size = @old_innodb_buffer_pool_size;
 set global innodb_file_per_table = @old_innodb_file_per_table;
-set global innodb_thread_concurrency = @old_innodb_thread_concurrency;
-set global innodb_thread_sleep_delay = @old_innodb_thread_sleep_delay;
 set global innodb_disable_resize_buffer_pool_debug = @old_innodb_disable_resize;
 --enable_query_log