Metadata getPrimaryKeys using like in place of strict equality

created after https://jira.mariadb.org/browse/MDEV-32915.

Javadoc indicate that parameters must be :
Parameters:

• catalog - a catalog name; must match the catalog name as it is stored in the database; "" retrieves those without a catalog; null means that the catalog name should not be used to narrow the search
• schema - a schema name; must match the schema name as it is stored in the database; "" retrieves those without a schema; null means that the schema name should not be used to narrow the search
• table - a table name; must match the table name as it is stored in the database
  But current implementation does do a pattern equality, so TABLE LIKE '<table>'. Table containing "_" will then do a pattern matching search in place of equality

At the same time, query can be improved, using INFORMATION_SCHEMA.STATISTICS table only. INFORMATION_SCHEMA.COLUMNS is redondant, since we can rely on INDEX_NAME='PRIMARY' to identify primary keys (user cannot create a non primary index with name 'PRIMARY')