Also support the SAMPLE aggregate in the lazy GROUP BY implementation

[RobinTF]

This aggregate function was missing so far in the common implementation of lazy and hash map based GROUP BY. The current implementation is rather simplistic, and can probably be improved, because for SAMPLE we can ignore all but the first entry of each group.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.32%. Comparing base (bed8b29) to head (204e6cb).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1511 +/- ## ========================================== + Coverage 94.30% 94.32% +0.01% ========================================== Files 350 351 +1 Lines 25920 25933 +13 Branches 3486 3489 +3 ========================================== + Hits 24445 24461 +16 + Misses 1433 1430 -3 Partials 42 42 ```

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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud