Align handling of dbGetQuery without parameters to odbc::odbc()

[andrjohns]

Using adbi with the adbcsnowflake snowflake driver currently fails to execute any queries unless the immediate = TRUE argument is set.

The odbc package automatically sets the immediate argument if the params argument is null, which also solves the error here

[andrjohns]

@krlmlr apologies for the ping, but does this fix look reasonable? We're looking to move to adbi & adbcsnowflake for our snowflake workflows, but needing to update our codebase to add immediate = TRUE for any queries to run is a bit of a blocker

[krlmlr]

Thanks. This change might be good for dbGetQuery() (and also dbExecute()), I'm not sure about dbSendQuery() and dbSendStatement() -- these seem to be kept as FALSE with odbc as well.

This is also something to review in the context of the DBI package: perhaps DBI could set this as a default too.