target_session_attrs cannot be used with replication connection

[thedolphin]

Describe the bug

target_session_attrs cannot be used with replication connection

To Reproduce

config, _ := pgconn.ParseConfig("target_session_attrs=read-write")
config.RuntimeParams["replication"] = "database"
pgConn, err := pgconn.ConnectConfig(ctx, config)
if err != nil {
    log.Print(err)
}

Expected behavior

Primary server was found and connection succeeded

Actual behavior

ValidateConnect failed: ERROR: extended query protocol not supported in a replication connection (SQLSTATE 08P01)

Version

• Go: go version go1.22.7 linux/amd64
• PostgreSQL: 16
• pgx: github.com/jackc/pgx/v5 v5.7.1

Additional context

Seems that ExecParams in ValidateConnectTargetSessionAttrs* functions is redundant and could be replaced with Exec function, while it triggers extended query protocol usage

pgx/pgconn/config.go

Line 864 in b9e2b20

result := pgConn.ExecParams(ctx, "show transaction_read_only", nil, nil, nil, nil).Read()