Performance degradation with CURRENT_DATE, LOCALTIME and LOCALTIMESTAMP

[asfernandes]

After introduction of time zones, request's cached timestamp started to be stored in the GMT time zone.

That made ~10x performance degradation to CURRENT_DATE, LOCALTIME and LOCALTIMESTAMP.

Test cases:

execute block
as
    declare n integer = 1;
    declare d date;
begin
    while (n < 1000000)
    do
    begin
        n = n + 1;
        d = current_date;
    end
end!


execute block
as
    declare n integer = 1;
    declare d time;
begin
    while (n < 1000000)
    do
    begin
        n = n + 1;
        d = localtime;
    end
end!


execute block
as
    declare n integer = 1;
    declare d timestamp;
begin
    while (n < 1000000)
    do
    begin
        n = n + 1;
        d = localtimestamp;
    end
end!