Exclude composite identifier columns from the UPDATE SET clause

[sharanggupta]

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Closes #2338

For an aggregate whose @Id is a composite identifier, SqlGenerator.Columns classified the identifier's columns as regular columns because it asked the property's owner (the identifier type itself, which has no @Id of its own) whether the property is the id. The columns consequently appeared in the SET clause of the generated UPDATE in addition to the WHERE clause, which fails on databases that reject assignments to primary key columns (the YDB dialect currently works around this downstream in ydb-platform/ydb-java-dialects#241).

The column walk now carries the attributes a property inherits from its enclosing properties (column prefix, insert-only, part of the identifier) in one small Nesting value instead of two parallel parameters, so columns reached through the @Id property are registered as identifier columns and excluded from SET. WHERE and INSERT are unchanged; the latter already receives the identifier columns from the parameter source. If you would rather keep the existing parameter style and just thread an additional flag, I am happy to change it.

Unit tests cover both declaration forms (@Id EmployeeId id in SqlGeneratorUnitTests, @Id @Embedded EmbeddedId in SqlGeneratorEmbeddedUnitTests); both fail on main. The spring-data-jdbc unit suite (590 tests) and the HSQL composite-id and embedded integration tests pass.