MDEV-22570 Implement wsrep_provider_options as plugin

- Provider options are read from the provider during
  startup, before plugins are initialized.
- New wsrep_provider plugin for which sysvars are generated
  dynamically from options read from the provider.
- The plugin is enabled by option plugin-wsrep-provider=ON.
  If enabled, wsrep_provider_options can no longer be used,
  (an error is raised on attempts to do so).
- Each option is either string, integer, double or bool
- Options can be dynamic / readonly
- Options can be deprecated

Limitations:

- We do not check that the value of a provider option falls
  within a certain range. This type of validation is still
  done in Galera side.

Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

mysql-test/suite/wsrep/r/wsrep_provider_plugin.result

@@ -0,0 +1,20 @@
+CREATE TABLE t1 (f1 INT PRIMARY KEY) ENGINE=InnoDB;
+SET GLOBAL wsrep_provider_repl_max_ws_size=1;
+SHOW VARIABLES LIKE 'wsrep_provider_repl_max_ws_size';
+Variable_name	Value
+wsrep_provider_repl_max_ws_size	1
+INSERT INTO t1 VALUES (1);
+ERROR HY000: Got error 5 "Input/output error" during COMMIT
+SET GLOBAL wsrep_provider_repl_max_ws_size=DEFAULT;
+SHOW VARIABLES LIKE 'wsrep_provider_repl_max_ws_size';
+Variable_name	Value
+wsrep_provider_repl_max_ws_size	2147483647
+INSERT INTO t1 VALUES (1);
+SET GLOBAL wsrep_provider_options='repl.max_ws_size=1';
+ERROR HY000: Variable 'wsrep_provider_options' is a read only variable
+INSERT INTO t1 VALUES (2);
+SET GLOBAL wsrep_provider='none';
+ERROR HY000: Variable 'wsrep_provider' is a read only variable
+DROP TABLE t1;
+CALL mtr.add_suppression("transaction size limit");
+CALL mtr.add_suppression("rbr write fail");

mysql-test/suite/wsrep/r/wsrep_provider_plugin_basic.result

@@ -0,0 +1,65 @@
+select variable_type, global_value from information_schema.system_variables where variable_name = 'wsrep_provider_socket_recv_buf_size';
+variable_type	global_value
+VARCHAR	auto
+set global wsrep_provider_socket_recv_buf_size = 'foo';
+ERROR 42000: Variable 'socket_recv_buf_size' can't be set to the value of 'foo'
+set global wsrep_provider_socket_recv_buf_size = '1M';
+show global variables like 'wsrep_provider_socket_recv_buf_size';
+Variable_name	Value
+wsrep_provider_socket_recv_buf_size	1M
+set global wsrep_provider_socket_recv_buf_size = default;
+show global variables like 'wsrep_provider_socket_recv_buf_size';
+Variable_name	Value
+wsrep_provider_socket_recv_buf_size	auto
+select variable_type, global_value from information_schema.system_variables where variable_name = 'wsrep_provider_evs_send_window';
+variable_type	global_value
+BIGINT	4
+set global wsrep_provider_evs_send_window = -10;
+ERROR 42000: Variable 'evs_send_window' can't be set to the value of '-10'
+set global wsrep_provider_evs_send_window = 10;
+show global variables like 'wsrep_provider_evs_send_window';
+Variable_name	Value
+wsrep_provider_evs_send_window	10
+set global wsrep_provider_evs_send_window = default;
+show global variables like 'wsrep_provider_evs_send_window';
+Variable_name	Value
+wsrep_provider_evs_send_window	4
+select variable_type from information_schema.system_variables where variable_name = 'wsrep_provider_gcs_max_throttle';
+variable_type
+DOUBLE
+set global wsrep_provider_gcs_max_throttle = 1.1;
+ERROR 42000: Variable 'gcs_max_throttle' can't be set to the value of '1.100000'
+set global wsrep_provider_gcs_max_throttle = 0.5;
+show global variables like 'wsrep_provider_gcs_max_throttle';
+Variable_name	Value
+wsrep_provider_gcs_max_throttle	0.500000
+set global wsrep_provider_gcs_max_throttle = default;
+show global variables like 'wsrep_provider_gcs_max_throttle';
+Variable_name	Value
+wsrep_provider_gcs_max_throttle	0.250000
+select variable_type from information_schema.system_variables where variable_name = 'wsrep_provider_cert_log_conflicts';
+variable_type
+BOOLEAN
+set global wsrep_provider_cert_log_conflicts = on;
+show global variables like 'wsrep_provider_cert_log_conflicts';
+Variable_name	Value
+wsrep_provider_cert_log_conflicts	ON
+set global wsrep_provider_cert_log_conflicts = off;
+show global variables like 'wsrep_provider_cert_log_conflicts';
+Variable_name	Value
+wsrep_provider_cert_log_conflicts	OFF
+set global wsrep_provider_cert_log_conflicts = default;
+show global variables like 'wsrep_provider_cert_log_conflicts';
+Variable_name	Value
+wsrep_provider_cert_log_conflicts	OFF
+select read_only from information_schema.system_variables where variable_name = 'wsrep_provider_evs_auto_evict';
+read_only
+YES
+set global wsrep_provider_evs_auto_evict = on;
+ERROR HY000: Variable 'wsrep_provider_evs_auto_evict' is a read only variable
+set global wsrep_provider_gcs_fc_master_slave = default;
+Warnings:
+Warning	1287	'@@wsrep_provider_gcs_fc_master_slave' is deprecated and will be removed in a future release
+call mtr.add_suppression("error setting param");
+call mtr.add_suppression("Unknown parameter");
+call mtr.add_suppression("Setting parameter");