Fix auto_increment metric collection errors caused by using collation in INFORMATION_SCHEMA searches

[nicolevv]

Hello, we have encountered the following issues in our actual production:

There are two tables in the database, test.x and test.X, which caused data collection failure.

Original error message:

An error has occurred while serving metrics:

4 error(s) occurred:
* collected metric "mysql_info_schema_auto_increment_column" { label:<name:"column" value:"id" > label:<name:"schema" value:"test" > label:<name:"table" value:"x" > gauge:<value:1 > } was collected before with the same name and label values
* collected metric "mysql_info_schema_auto_increment_column_max" { label:<name:"column" value:"id" > label:<name:"schema" value:"test" > label:<name:"table" value:"x" > gauge:<value:4.294967295e+09 > } was collected before with the same name and label values
* collected metric "mysql_info_schema_auto_increment_column" { label:<name:"column" value:"id" > label:<name:"schema" value:"test" > label:<name:"table" value:"X" > gauge:<value:1 > } was collected before with the same name and label values
* collected metric "mysql_info_schema_auto_increment_column_max" { label:<name:"column" value:"id" > label:<name:"schema" value:"test" > label:<name:"table" value:"X" > gauge:<value:4.294967295e+09 > } was collected before with the same name and label values

The result set obtained from the original SQL query on the database is as follows:

MySQL instance parameters:

lower_case_file_system=off
lower_case_file_system=0

The data of the two tables with different cases, x and X, will appear twice separately. This caused the data collection to fail, and the relevant metrics for that node could not be collected. The table_schema and table_name need to be treated as case-sensitive unique keys for association.

References:

https://bugs.mysql.com/bug.php?id=34921

https://dev.mysql.com/doc/refman/5.7/en/charset-collation-information-schema.html