Bug #57243 Inconsistent use of trans_register_ha() API in InnoDB

Remove trx_t::active_trans. Split into two separate fields with distinct
responsibilities. trx_t::is_registered and trx_t::owns_prepare_mutex.
There are wrapper functions for using this fields in ha_innodb.cc. The
wrapper functions check for invariants.

Fix some formatting to conform to InnoDB guidelines.

Remove innobase_register_stmt() and innobase_register_trx_and_stmt().

Add:
trx_is_started()
trx_deregister_from_2pc()
trx_register_for_2pc()
trx_is_registered_for_2pc()
trx_owns_prepare_commit_mutex_set()
trx_has_prepare_commit_mutex()

rb://479, Approved by Jimmy Yang.

storage/innobase/include/trx0trx.h

@@ -470,6 +470,20 @@ struct trx_struct{
 					of view of concurrency control:
 					TRX_ACTIVE, TRX_COMMITTED_IN_MEMORY,
 					... */
+	/*------------------------------*/
+	/* MySQL has a transaction coordinator to coordinate two phase
+       	commit between multiple storage engines and the binary log. When
+       	an engine participates in a transaction, it's responsible for
+       	registering itself using the trans_register_ha() API. */
+	unsigned	is_registered:1;/* This flag is set to 1 after the
+				       	transaction has been registered with
+				       	the coordinator using the XA API, and
+				       	is set to 0 after commit or rollback. */
+	unsigned	owns_prepare_mutex:1;/* 1 if owns prepare mutex, if
+					this is set to 1 then registered should
+					also be set to 1. This is used in the
+					XA code */
+	/*------------------------------*/
 	ulint		isolation_level;/* TRX_ISO_REPEATABLE_READ, ... */
 	ulint		check_foreigns;	/* normally TRUE, but if the user
 					wants to suppress foreign key checks,
@@ -500,9 +514,6 @@ struct trx_struct{
 					in that case we must flush the log
 					in trx_commit_complete_for_mysql() */
 	ulint		duplicates;	/*!< TRX_DUP_IGNORE | TRX_DUP_REPLACE */
-	ulint		active_trans;	/*!< 1 - if a transaction in MySQL
-					is active. 2 - if prepare_commit_mutex
-					was taken */
 	ulint		has_search_latch;
 					/* TRUE if this trx has latched the
 					search system latch in S-mode */

storage/innobase/trx/trx0trx.c

@@ -105,7 +105,11 @@ trx_create(
 	trx->is_purge = 0;
 	trx->is_recovered = 0;
 	trx->conc_state = TRX_NOT_STARTED;
-	trx->start_time = time(NULL);
+
+	trx->is_registered = 0;
+	trx->owns_prepare_mutex = 0;
+
+	trx->start_time = ut_time();
 
 	trx->isolation_level = TRX_ISO_REPEATABLE_READ;
 
@@ -124,7 +128,6 @@ trx_create(
 	trx->table_id = 0;
 
 	trx->mysql_thd = NULL;
-	trx->active_trans = 0;
 	trx->duplicates = 0;
 
 	trx->n_mysql_tables_in_use = 0;