Support configuration parameters handling

[jennifersp]

This PR includes changes for:

• The complete list of configuration parameters is in.
• All of the postgres configuration parameters will be added to existing system variables list in GMS. There are two parameters that have the same name as mysql system variables, which will be overwritten by the postgres parameter. This is temporary until we completely separate the use of them.
• Current implementation of sql.SystemVariableRegistry interface is for Dolt only, but we add all the postgres configuration parameters to the SystemVariables global variable in GMS. This should be updated to handle Doltgres config parameters separately in future.
• The default and only supported scope of postgres parameters is SESSION, which is used as SESSION scope in GMS. There is no GLOBAL scope in postgres to be set during a session.

Depends on GMS PR: dolthub/go-mysql-server#2375
Depends on Dolt PR: dolthub/dolt#7579

Next up:

• need more support for Parameter such as accept setting memory and time values that has unit information, etc.
• need privileges and role checking for specific parameters.
• support setting parameter defaults from configuration file.
• `LOCAL scope support.

[Hydrocharged]

Overall looks good! Great work!

[Hydrocharged]

LGTM! Great work!