Parse MySQL `SET GLOBAL` variables

[mvzink]

In addition to SESSION and LOCAL qualifiers, MySQL allows GLOBAL for modifying system variables:

mysql> SET GLOBAL max_connections = 1000;
Query OK, 0 rows affected (0.00 sec)

sqlparser currently interprets global as a variable name and fails to parse:

$ echo -n "SET GLOBAL max_connections = 1000;" | cargo run --example cli - --mysql
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.02s
     Running `target/debug/examples/cli - --mysql`
Parsing from stdin using MySqlDialect
2025-01-31T00:44:22.858Z DEBUG [sqlparser::parser] Parsing sql 'SET GLOBAL max_connections = 1000;'...
Error during parsing: ParserError("Expected: equals sign or TO, found: max_connections at Line: 1, Column: 12")

[mvzink]

As mentioned in #1696, this may be best accomplished in combination with #1697; possibly this issue should just be closed in favor of that one.

[mvzink]

Oops, looks like #1757 marked this as closed when it should have marked #1697 as closed. I don't have permissions to reopen this; are you able to @iffyio ?