[KYUUBI #7789] Bump Paimon 2.1.0 and enable Paimon tests for Spark 4.1

### Why are the changes needed?

Paimon 1.4.2 has no Spark 4.1 build, so the Spark 4.1 profile had to depend on the Spark 4.0 artifact (`paimon-spark-4.0_2.13`) and keep `PaimonTest` excluded. Paimon 2.1.0 ships `paimon-spark-4.1_2.13`, which unblocks running the Paimon authz suite on Spark 4.1.

- `paimon.version` 1.4.2 -> 2.1.0 and `paimon.artifact` -> `paimon-spark-${spark.binary.version}_${scala.binary.version}` for the Spark 4.1/4.2/4.3 profiles
- Spark 4.1: drop `org.apache.kyuubi.tags.PaimonTest` from `maven.plugin.scalatest.exclude.tags`
- Spark 4.2/4.3: `PaimonTest` stays excluded; both profiles alias `spark.binary.version` to 4.1, so they keep resolving `paimon-spark-4.1_2.13`
- Spark 4.0 keeps Paimon 1.4.2: the Spark 4.0 build of Paimon 2.x declares Spark 4.0.3, but its classes reference the Spark 4.1-only `org.apache.spark.sql.connector.catalog.constraints.Constraint` (`Table.constraints()`), so it cannot run on Spark 4.0

### How was this patch tested?

`PaimonCatalogRangerSparkExtensionSuite`, Java 17 and Scala 2.13:

- Spark 4.1.2 + Paimon 2.1.0: 37/37 passed
- Spark 4.0.3 + Paimon 1.4.2: 37/37 passed
- Spark 4.0.3 + Paimon 2.0.0 and 2.1.0: fails with `NoClassDefFoundError: org.apache.spark.sql.connector.catalog.constraints.Constraint`, raised inside the authz reflection helper - hence the Spark 4.0 profile stays on 1.4.2

`HiveCatalogRangerSparkExtensionSuite` on Spark 4.1.2 + Paimon 2.1.0: 53/53 passed.

```
build/mvn -B test -pl extensions/spark/kyuubi-spark-authz -am -Pspark-4.1 -Pscala-2.13 -Pspark-provided \
    -Dtest=none -DwildcardSuites=org.apache.kyuubi.plugin.spark.authz.ranger.PaimonCatalogRangerSparkExtensionSuite
```

### Was this patch assisted by generative AI tooling?

Assisted-by: Codex with gemini-4-argon

Closes #7789 from pan3793/paimon-2.1.

Closes #7789

c84ee87 [Cheng Pan] nit: fix comment wording
25f329c [Cheng Pan] nit
c24af36 [Cheng Pan] Bump Paimon 2.1.0 and enable Paimon tests for Spark 4.1

Authored-by: Cheng Pan <pan3793@gmail.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>

Author: pan3793

pom.xml

@@ -2080,6 +2080,8 @@
                 <delta.version>4.3.1</delta.version>
                 <delta.artifact>delta-spark_${spark.binary.version}_${scala.binary.version}</delta.artifact>
                 <hudi.version>1.2.0</hudi.version>
+                <!-- Paimon 2.x references the Spark 4.1+ Table.constraints() API in its Spark 4.0
+                     build, causing java.lang.NoClassDefFoundError at runtime. -->
                 <paimon.version>1.4.2</paimon.version>
                 <paimon.artifact>paimon-spark-${spark.binary.version}_${scala.binary.version}</paimon.artifact>
                 <!-- Exclude SparkLocalClusterTest due to Scala 2.13.17 changes serialVersionUID of scala.collection.immutable.ArraySeq -->
@@ -2103,10 +2105,9 @@
                 <delta.version>4.3.1</delta.version>
                 <delta.artifact>delta-spark_${spark.binary.version}_${scala.binary.version}</delta.artifact>
                 <hudi.version>1.2.0</hudi.version>
-                <!-- TODO: update once Paimon support Spark 4.1. -->
-                <paimon.version>1.4.2</paimon.version>
-                <paimon.artifact>paimon-spark-4.0_${scala.binary.version}</paimon.artifact>
-                <maven.plugin.scalatest.exclude.tags>org.scalatest.tags.Slow,org.apache.kyuubi.tags.PaimonTest</maven.plugin.scalatest.exclude.tags>
+                <paimon.version>2.1.0</paimon.version>
+                <paimon.artifact>paimon-spark-${spark.binary.version}_${scala.binary.version}</paimon.artifact>
+                <maven.plugin.scalatest.exclude.tags>org.scalatest.tags.Slow</maven.plugin.scalatest.exclude.tags>
                 <spark.archive.name>spark-${spark.version}-bin-hadoop3.tgz</spark.archive.name>
             </properties>
         </profile>
@@ -2132,8 +2133,8 @@
                 <delta.artifact>delta-spark_${spark.binary.version}_${scala.binary.version}</delta.artifact>
                 <hudi.version>1.2.0</hudi.version>
                 <!-- TODO: update once Paimon support Spark 4.2. -->
-                <paimon.version>1.4.2</paimon.version>
-                <paimon.artifact>paimon-spark-4.0_${scala.binary.version}</paimon.artifact>
+                <paimon.version>2.1.0</paimon.version>
+                <paimon.artifact>paimon-spark-${spark.binary.version}_${scala.binary.version}</paimon.artifact>
                 <maven.plugin.scalatest.exclude.tags>org.scalatest.tags.Slow,org.apache.kyuubi.tags.DeltaTest,org.apache.kyuubi.tags.IcebergTest,org.apache.kyuubi.tags.PaimonTest,org.apache.kyuubi.tags.HudiTest</maven.plugin.scalatest.exclude.tags>
                 <spark.archive.name>spark-${spark.version}-bin-hadoop3.tgz</spark.archive.name>
             </properties>
@@ -2161,8 +2162,8 @@
                 <delta.artifact>delta-spark_${spark.binary.version}_${scala.binary.version}</delta.artifact>
                 <hudi.version>1.2.0</hudi.version>
                 <!-- TODO: update once Paimon support Spark 4.3. -->
-                <paimon.version>1.4.2</paimon.version>
-                <paimon.artifact>paimon-spark-4.0_${scala.binary.version}</paimon.artifact>
+                <paimon.version>2.1.0</paimon.version>
+                <paimon.artifact>paimon-spark-4.1_${scala.binary.version}</paimon.artifact>
                 <maven.plugin.scalatest.exclude.tags>org.scalatest.tags.Slow,org.apache.kyuubi.tags.DeltaTest,org.apache.kyuubi.tags.IcebergTest,org.apache.kyuubi.tags.PaimonTest,org.apache.kyuubi.tags.HudiTest</maven.plugin.scalatest.exclude.tags>
                 <!-- TODO remove once Spark 4.3.0 GA -->
                 <spark.archive.mirror>https://dist.apache.org/repos/dist/dev/spark/v4.3.0-rc2-bin</spark.archive.mirror>