Add missing UInt128 (UUID) field visitors

[simPod]

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TBH, I have just a little idea what I have done here but I tried to address those #1770, #2611

It is not possible to use UUID in WHERE condition. I tried to implement it but need help with that. Not sure if the way I have tried to do this is the right way and whether I should continue, until I resolve all errors or whether it needs another solution.

[alexey-milovidov]

That looks mostly correct.

Only few issues remain:

1. I cannot find implementation of FieldVisitorToString for UInt128. That will likely require some effort.
2. Comparison (less/greater) operators for UInt128 may work even with your implementation (that returns false when comparing with other integer type) but it will confuse index when user write something like x > 1 where x is UInt128. Better to provide correct implementation from the beginning.

[alexey-milovidov]

.

[simPod]

1. it's implemented in https://github.com/yandex/ClickHouse/blob/master/dbms/src/Functions/FunctionsCoding.h#L893, couldn't it be somehow leveraged?
2. hm, I'm afraid I'm out of skill for that, first time editing C code. Maybe someone can cherrypick and continue the work here?

[alexey-milovidov]

The implementation is still incomplete, but it is better than nothing and now #2611 is fixed.