Update contrib/datasketches-cpp to 5.2.0 and backport the HLL union fix

Backport of ClickHouse/ClickHouse@a067567, re-created
here rather than cherry-picked so that it carries a sign-off.

The submodule tracked `apache/datasketches-cpp` directly, pinned to `76edd74f`
(2024-05-16), an upstream development commit. It moves onto a `ClickHouse/`-prefixed
branch of our fork, the way `docs/development/contrib` asks:

    ClickHouse/datasketches-cpp, branch ClickHouse/5.2.0
      de8553ba  5.2.0, the newest upstream release (2025-01-15)
      23bd9b07  backport of apache/datasketches-cpp#512

apache/datasketches-cpp#512 is the HyperLogLog union fix. No upstream release carries
it, so it is cherry-picked onto the `5.2.0` tag there. `uniqApacheHLL`, added next,
needs it: without it a merged HLL sketch reports a wrong estimate and serializes a
state that other DataSketches implementations read differently.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: UnamedRus <dtitmoav@gmail.com>

Author: UnamedRus

.gitmodules

@@ -154,7 +154,7 @@
 	url = https://github.com/ClickHouse/NuRaft
 [submodule "contrib/datasketches-cpp"]
 	path = contrib/datasketches-cpp
-	url = https://github.com/apache/datasketches-cpp
+	url = https://github.com/ClickHouse/datasketches-cpp
 [submodule "contrib/yaml-cpp"]
 	path = contrib/yaml-cpp
 	url = https://github.com/ClickHouse/yaml-cpp

contrib/datasketches-cpp

@@ -0,0 +1 @@
+16	16	30

tests/queries/0_stateless/05055_uniq_theta_compressed_state.reference

@@ -0,0 +1,22 @@
+-- Tags: no-fasttest
+-- - no-fasttest -- compiled w/o datasketches
+
+-- Apache DataSketches can serialize a Theta sketch in a compressed form (serialization
+-- version 4) that packs the retained values at a variable number of bits per entry.
+-- ClickHouse always writes the uncompressed form, but it has to read the compressed one,
+-- because an `AggregateFunction(uniqTheta, ...)` state can come from another
+-- implementation of the library. Two of the unpacking routines decoded it incorrectly,
+-- and the result was a silently too low estimate rather than an error.
+
+-- Both states below are canonical compressed encodings of a sketch that retains 16 values
+-- with theta = 1, so the estimate is exact. The first packs its values at 33 bits per
+-- entry and the second at 35; the two widths are decoded by separate routines. The two
+-- sketches have exactly two values in common, so their union retains 30.
+
+WITH
+    CAST(unhex('4B01040321011ACC9310000001F4000000FA0000007D0000003E8000001F4000000FA0000007D180000000000001F4000000FA0000007D0000003E8000001F4000000FA0000007D0000003E8') AS AggregateFunction(uniqTheta, UInt64)) AS state_33_bits,
+    CAST(unhex('4F01040323011ACC93100000007D0000000FA1000000004000000000000007D0000000FA0000001F40000003E80000007D0000000FA1000000000000003E80000007D0000000FA0000001F40000003E8') AS AggregateFunction(uniqTheta, UInt64)) AS state_35_bits
+SELECT
+    finalizeAggregation(state_33_bits),
+    finalizeAggregation(state_35_bits),
+    finalizeAggregation(uniqThetaUnion(state_33_bits, state_35_bits));