Fix distributed table with a constant sharding key

[vitlibar]

Changelog category:

• Bug Fix

Changelog entry:

Fix distributed table with a constant sharding key.

Closes #59589

[vitlibar]

A constant sharding key is not very useful but still valid. We must not crash on it.

[robot-ch-test-poll]

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[vitlibar]

Function StorageDistributed::createSelector() must return a vector specifying how to split the input block into blocks for each shard according to values of the sharding key. The size of a returned vector must be the same as the number of rows in the input block and must be equal to the number of rows in the result.column.

This replacement column = &col_const->getDataColumn() here was wrong because it caused the returned selector to have only one element. Also this replacement was unnecessary because below in this function the createBlockSelector() function is called which knows how to deal with const columns (see). Thus in this PR I'm just removing this unnecessary and wrong code.

[Algunenano]

This has broken multiple tests with the analyzer (or at least the've become flaky):