Many InnoDB data dictionary cache operations require that the
table name be copied so that it will be NUL terminated.
(For example, SYS_TABLES.NAME is not guaranteed to be NUL-terminated.)

dict_table_t::is_garbage_name(): Check if a name belongs to
the background drop table queue.

dict_check_if_system_table_exists(): Remove.

dict_sys_t::load_sys_tables(): Load the non-hard-coded system tables
SYS_FOREIGN, SYS_FOREIGN_COLS, SYS_VIRTUAL on startup.

dict_sys_t::create_or_check_sys_tables(): Replaces
dict_create_or_check_foreign_constraint_tables() and
dict_create_or_check_sys_virtual().

dict_sys_t::load_table(): Replaces dict_table_get_low()
and dict_load_table().

dict_sys_t::find_table(): Renamed from get_table().

dict_sys_t::sys_tables_exist(): Check whether all the non-hard-coded
tables SYS_FOREIGN, SYS_FOREIGN_COLS, SYS_VIRTUAL exist.

trx_t::has_stats_table_lock(): Moved to dict0stats.cc.

Some error messages will now report table names in the internal
databasename/tablename format, instead of `databasename`.`tablename`.