[Feature]: Support User Impersonation for Iceberg REST Catalog

[nqvuong1998]

Description

User Impersonation enables the REST catalog to perform actions on behalf of a specified user. This feature allows clients to impersonate users when interacting with the Iceberg catalog, ensuring that actions are executed with the appropriate user permissions. It enhances security by allowing fine-grained access control, enabling the system to enforce authorization policies based on the impersonated user's identity. This is particularly useful in multi-tenant environments where different users or applications may require different levels of access to data stored in Iceberg tables.

Expected Use Cases

Same as Hive Metastore:

• Spark + REST Catalog: --proxy-user
• Trino + REST Catalog: impersonation.enabled

Requested Changes in public API

No response

[nqvuong1998]

cc @snazy @ajantha-bhat