[Subtask] support UpdateColumnNullable in AlterTable for spark connector

[FANNG1]

Describe the subtask

please add related code to com.datastrato.gravitino.spark.catalogGravitinoCatalog.java, transfrom Spark TableChange to Gravitino TableChange, you could refer to #2502 , Hive doesn't support update column nullable for now, so no need to add integrate test.
public Table alterTable(Identifier ident, TableChange... changes) throws NoSuchTableException { }

Parent issue

#1227

[ichuniq]

Hi I would like to work on this! However, could you elaborate on

Hive doesn't support update column nullable for now, so no need to add integrate test.

What I understand now is that I probably should add testAlterTableUpdateColumnNullability() in SparkCommonIT.java like the referenced PR did, alongside with converting spark TableChange.UpdateColumnNullavility() and adding its unit test. Did I miss anything? Thanks!

[FANNG1]

@ichuniq , you needn't add testAlterTableUpdateColumnNullability() in SparkCommonIT.java, because it wouldn't work. you only need to implement convert logic and add unit test.