MDEV-19940 Clean up INFORMATION_SCHEMA.INNODB_ tables

Shorten some VARCHAR attributes to a more reasonable length.

INNODB_METRICS: Rename the column STATUS to ENABLED, and make it Boolean.

Replace with INT(1) many Boolean attributes that were declared as VARCHAR
containing 'NO','YES','disabled','enabled','Uninitialized','Initialized'.

Replace some VARCHAR attributes with ENUM.

Replace some BIGINT with INT when 32 bits are sufficient.

Remove INNODB_SYS_TABLESPACES.SPACE_TYPE. The type of a tablespace
can be derived from the tablespace ID. A fixed number is used for
the system tablespace and the temporary tablespace. All other tablespaces
are single-table or single-partition tablespaces.

i_s_locks_row_t::lock_type, lock_get_type_str(): Remove.
This is a redundant field. Table and record locks can be
distinguished by whether i_s_locks_row_t::lock_index is NULL.

fill_trx_row(): Do not unnecessarily copy the constant strings that
trx->op_info is pointing to.

i_s_locks_row_t::lock_mode: Replace string with integer.

lock_get_mode_str(), lock_get_trx_id(), lock_get_trx(): Remove.

field_store_ulint(): Remove.

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

@@ -22,7 +22,7 @@ lock_table	COUNT(*)
 "test"."t_min"	2
 "test"."`t'\""_str"	10
 Field	Type	Null	Key	Default	Extra
-trx_id	varchar(18)	NO			
+trx_id	bigint(21) unsigned	NO		0	
 trx_state	varchar(13)	NO			
 trx_started	datetime	NO		0000-00-00 00:00:00	
 trx_requested_lock_id	varchar(81)	YES		NULL	
@@ -38,7 +38,7 @@ trx_lock_memory_bytes	bigint(21) unsigned	NO		0
 trx_rows_locked	bigint(21) unsigned	NO		0	
 trx_rows_modified	bigint(21) unsigned	NO		0	
 trx_concurrency_tickets	bigint(21) unsigned	NO		0	
-trx_isolation_level	varchar(16)	NO			
+trx_isolation_level	enum('READ UNCOMMITTED','READ COMMITTED','REPEATABLE READ','SERIALIZABLE')	NO			
 trx_unique_checks	int(1)	NO		0	
 trx_foreign_key_checks	int(1)	NO		0	
 trx_last_foreign_key_error	varchar(256)	YES		NULL