Support for Postgres's CREATE SERVER

[solontsev]

Closes #1814

[iffyio]

Suggested change

&& dialect_of!(self is PostgreSqlDialect | GenericDialect)

I think it should be fine to let the parser be permissive and accept this statement whenever it shows up

[iffyio]

Suggested change

	pub struct ServerOption {
	pub struct CreateServerOption {

[iffyio]

For new statements we're moving away from using anonymous structs, here can we introduce a dedicated struct for this statement?

CreateServer(CreateServerStatement)

See Statement::Raise as an example

[iffyio]

Can we rename this to something more descriptive e.g. explicitly foreign_data_wrapper?

[iffyio]

Suggested change

	/// ```sql
	/// CREATE SERVER [ IF NOT EXISTS ] server_name [ TYPE 'server_type' ] [ VERSION 'server_version' ]
	/// FOREIGN DATA WRAPPER fdw_name
	/// [ OPTIONS ( option 'value' [, ... ] ) ]
	/// ```
	///
	/// [PostgreSQL Documentation](https://www.postgresql.org/docs/current/sql-createserver.html)
	pub fn parse_pg_create_server(&mut self) -> Result<Statement, ParserError> {
	/// Parse a `CREATE SERVER` statement.
	///
	/// See [Statement::CreateServer]
	pub fn parse_pg_create_server(&mut self) -> Result<Statement, ParserError> {

I think we can do something like this to avoid duplicating the comments. The syntax we can skip entirely since that should be covered by the doc link if the reader requires further context