MDEV-29983 Deprecate innodb_file_per_table

Before commit 6112853cda in MySQL 4.1.1
introduced the parameter innodb_file_per_table, all InnoDB data was
written to the InnoDB system tablespace (often named ibdata1).
A serious design problem is that once the system tablespace has grown to
some size, it cannot shrink even if the data inside it has been deleted.

There are also other design problems, such as the server hang MDEV-29930
that should only be possible when using innodb_file_per_table=0 and
innodb_undo_tablespaces=0 (storing both tables and undo logs in the
InnoDB system tablespace).

The parameter innodb_change_buffering was deprecated
in commit b5852ffbee.
Starting with commit baf276e6d4
(MDEV-19229) the number of innodb_undo_tablespaces can be increased,
so that the undo logs can be moved out of the system tablespace
of an existing installation.

If all these things (tables, undo logs, and the change buffer) are
removed from the InnoDB system tablespace, the only variable-size
data structure inside it is the InnoDB data dictionary.

DDL operations on .ibd files was optimized in
commit 86dc7b4d4c (MDEV-24626).
That should have removed any thinkable performance advantage of
using innodb_file_per_table=0.

Since there should be no benefit of setting innodb_file_per_table=0,
the parameter should be deprecated. Starting with MySQL 5.6 and
MariaDB Server 10.0, the default value is innodb_file_per_table=1.

mysql-test/suite/innodb_zip/r/innodb-zip.result

@@ -6,7 +6,10 @@ WHERE table_schema='mysqltest_innodb_zip';
 table_name	row_format	data_length	index_length
 SET @save_innodb_stats_on_metadata=@@global.innodb_stats_on_metadata;
 set session innodb_strict_mode=0;
+SET @save_fpt=@@GLOBAL.innodb_file_per_table;
 set global innodb_file_per_table=off;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
 SET @@global.innodb_stats_on_metadata=ON;
 create table t0(a int primary key) engine=innodb row_format=compressed;
 Warnings:
@@ -32,6 +35,8 @@ Warnings:
 Warning	1478	InnoDB: KEY_BLOCK_SIZE requires innodb_file_per_table.
 Warning	1478	InnoDB: ignoring KEY_BLOCK_SIZE=1.
 set global innodb_file_per_table=on;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
 create table t6(a int primary key) engine=innodb
 key_block_size=1 row_format=redundant;
 Warnings:
@@ -153,7 +158,6 @@ count(*)
 1
 update t1 set c3 = repeat('E', 20000) where c1 = 1;
 drop table t1;
-set global innodb_file_per_table = on;
 set innodb_strict_mode = off;
 create table t1 (id int primary key) engine = innodb key_block_size = 0;
 drop table t1;
@@ -247,6 +251,8 @@ Warning	1030	Got error 140 "Wrong create options" from storage engine InnoDB
 SELECT table_schema, table_name, row_format, data_length, index_length FROM information_schema.tables WHERE engine='innodb' AND table_schema != 'mysql' and table_schema != 'sys' order by table_name;
 table_schema	table_name	row_format	data_length	index_length
 set global innodb_file_per_table = off;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
 create table t1 (id int primary key) engine = innodb key_block_size = 1;
 ERROR HY000: Can't create table `mysqltest_innodb_zip`.`t1` (errno: 140 "Wrong create options")
 show warnings;
@@ -286,4 +292,8 @@ mysqltest_innodb_zip	t7	Dynamic	{valid}	0
 mysqltest_innodb_zip	t8	Compact	{valid}	0
 mysqltest_innodb_zip	t9	Redundant	{valid}	0
 drop table t7, t8, t9;
+SET GLOBAL innodb_file_per_table=@save_fpt;
+Warnings:
+Warning	1287	'@@innodb_file_per_table' is deprecated and will be removed in a future release
+SET @@global.innodb_stats_on_metadata=@save_innodb_stats_on_metadata;
 DROP DATABASE mysqltest_innodb_zip;