[CALCITE-6522] MAP_KEYS and MAP_VALUES function should throw if a key value is null

[caicancai]

https://issues.apache.org/jira/browse/CALCITE-6522

[caicancai]

cala> val df = spark.sql("select map_values(map(cast(null as int),0, 'foo', 1))");
df: org.apache.spark.sql.DataFrame = [map_values(map(CAST(NULL AS INT), 0, foo, 1)): array<int>]

scala> df.show()
org.apache.spark.SparkRuntimeException: [NULL_MAP_KEY] Cannot use null as map key.
at org.apache.spark.sql.errors.QueryExecutionErrors$.nullAsMapKeyNotAllowedError(QueryExecutionErrors.scala:445)

From the spark log, the error is reported at runtime, not parameter verification.
Similar to the previous 6400

[julianhyde]

There's a tab or multiple spaces in the jira case summary, commit message, PR summary. Please fix.

[caicancai]

There's a tab or multiple spaces in the jira case summary, commit message, PR summary. Please fix.

done

[sonarcloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[mihaibudiu]

There's error-prone error which has to be fixed.

[caicancai]

@mihaibudiu @julianhyde Sorry for the late fix, I'm on vacation and have time to fix this PR.
Can you review this PR for me if you have time?

[caicancai]

@mihaibudiu I squashed the commit and this problem may be solved in 1.38

[sonarcloud]

Quality Gate passed

Issues
7 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud