Create less emptyResults in sqlite3#execute

[enebo]

This should create less empty result arrays if there are multiple insert/update/deletes.

[enebo]

@seuros Just look this over. I am not sure my second comment is possible using JDBC since if I try to look ahead I got an inconsistent state error. I guess it makes sense that I cannot look at next one until I process resultset of current one.

[seuros]

I just realized we are operating on the driver not the adapter.

If we targeting only ActiveRecord, then this seems enough since AR always execute one SQL statement per exec_query.

if (hasResultSet) {
    try (ResultSet resultSet = statement.getResultSet()) {
        return mapQueryResult(context, connection, resultSet);
    }
} else {
    return newEmptyResult(context);
}

If we want to keep mirroring pg gem

IRubyObject result = newEmptyResult(context);

do {
    if (hasResultSet) {
        try (ResultSet rs = statement.getResultSet()) {
            result = mapQueryResult(context, connection, rs);
        }
    } else {
        result = newEmptyResult(context);
    }

    hasResultSet = statement.getMoreResults();
    updateCount = statement.getUpdateCount();
} while (hasResultSet || updateCount != -1);

return result;

[enebo]

@seuros I think we can mirror pg since we have some minor and unofficial pg support for mini_sql (not sure if it even works any more but it may be worth it to keep it).

[enebo]

@seuros adopted your changes from comment but the original intent is still here result == null so we are not alloc'ing n extra arrays.