Support query attributed in client protocol since 8.0.23

[kafka1991]

Feature Request

Is your feature request related to a problem? Please describe:

Improve compatibility with mysql 8.0 query attribute feature, both for protocol and build-in function.
Query Attributes document
Details of protocol: https://archive.fosdem.org/2021/schedule/event/mysql_protocl/attachments/slides/4274/export/events/attachments/mysql_protocl/slides/4274/FOSDEM21_MySQL_Protocols_Query_Attributes.pdf

Describe the feature you'd like:

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[dveeden]

I've added this to #7968 under "8.0.23"

[dveeden]

I think this is needed to be able to support this:

• Define CLIENT_QUERY_ATTRIBUTES
• Set CLIENT_QUERY_ATTRIBUTES in the Server Greeting
• Handle COM_QUERY with query attributes
• Handle COM_STMT_EXECUTE with query attributes
• Create a mysql_query_attribute_string() function

Optional:

• Use query attributes to set specific labels in metrics
• Use query attributes to change configuration on a per-query basis
• ...