The original motivation for this commit was that shared_ptr_helper used
std::shared_ptr<>() which does two heap allocations instead of
make_shared<>() which does a single allocation. Turned out that
1. the affected code (--> Storages/) is not on a hot path (rendering the
performance argument moot ...)
2. yet copying Storage objects is potentially dangerous and was
previously allowed.
Hence, this change
- removes shared_ptr_helper and as a result all inherited create() methods,
- instead, Storage objects are now created using make_shared<>() by the
caller (for that to work, many constructors had to be made public), and
- all Storage classes were marked as noncopyable using boost::noncopyable.
In sum, we are (likely) not making things faster but the code becomes
cleaner and harder to misuse.
This table adds a new table called the `time_zones` table:
```
:) select * from system.time_zones limit 10;
SELECT *
FROM system.time_zones
LIMIT 10
┌─time_zone──────────┐
│ Africa/Abidjan │
│ Africa/Accra │
│ Africa/Addis_Ababa │
│ Africa/Algiers │
│ Africa/Asmara │
│ Africa/Asmera │
│ Africa/Bamako │
│ Africa/Bangui │
│ Africa/Banjul │
│ Africa/Bissau │
└────────────────────┘
10 rows in set. Elapsed: 0.012 sec.
```
The available timezones are parsed from under
`ClickHouse/contrib/cctz/testdata/zoneinfo` through a script
and the table content is constructed from the
StorageSystemTimeZones.generated.cpp`.
I was able to test this locally and was able to get a list of time
zones as shown above.
