Core: Implement IRC Events endpoint request and response objects

[visit2rahul]

Closes #13580

Summary

Implements the core request, response, and model objects for the IRC Events endpoint
as defined in the REST Catalog specification (PR #12584).

Request / Response

• QueryEventsRequest — all filter fields (continuation token, page size, timestamp,
  operation types, catalog objects by name/ID, object types, custom filters)
• QueryEventsResponse — pagination token, highest processed timestamp, event list

Event Model

• Event — event ID, request ID, request event count, timestamp, actor, and
  polymorphic operation
• CatalogOperation — base interface with operationType() discriminator
• CatalogOperationParser — polymorphic serialization/deserialization with
  forward compatibility for unknown operation types

All 13 Operation Types

• Namespace: CreateNamespaceOperation, DropNamespaceOperation,
  UpdateNamespacePropertiesOperation
• Table: CreateTableOperation, RegisterTableOperation, DropTableOperation,
  UpdateTableOperation, RenameTableOperation
• View: CreateViewOperation, DropViewOperation, UpdateViewOperation,
  RenameViewOperation
• Extension: CustomOperation (for catalog-specific x- prefixed operations)

Serialization

• Parser classes for request, response, and events using JsonGenerator/JsonNode
• Reuses existing TableIdentifierParser, MetadataUpdateParser, and
  UpdateRequirementParser
• Jackson serializer/deserializer registration in RESTSerializers

Test Plan

• Round-trip serialization tests for all 13 operation types
• Round-trip tests for QueryEventsRequest (empty, partial, all fields)
• Round-trip tests for QueryEventsResponse (with events, empty)
• Forward compatibility test — unknown operation types deserialize gracefully
• Null/error input handling tests
• ./gradlew :iceberg-core:compileJava passes
• ./gradlew :iceberg-core:test passes (17 new tests)

[visit2rahul]

Quick context for reviewers — this issue has been attempted twice before:

• Core: Add Events REST endpoint with request/response objects (#13580) #13940 (@Narendra9793) — closed unmerged
• Core: IRC: Implement Events Endpoint Request & Response Objects #14142 (@aheev) — closed unmerged after extended inactivity

Both are now closed, so this is the only active PR for #13580.

@nastra — your earlier review on #14142 laid out four concrete requirements. Mapping each to this PR for ease of review:

1. ✅ Request/response classes in their respective packages

   • core/src/main/java/org/apache/iceberg/rest/requests/QueryEventsRequest.java
   • core/src/main/java/org/apache/iceberg/rest/responses/QueryEventsResponse.java

2. ✅ Separate JSON parser classes with tests

   • Parsers: QueryEventsRequestParser, QueryEventsResponseParser, EventParser, CatalogOperationParser
   • Tests: TestQueryEventsRequestParser, TestQueryEventsResponseParser, TestEventParser

3. ✅ Parsers registered in RESTSerializers

   • core/src/main/java/org/apache/iceberg/rest/RESTSerializers.java updated

4. ✅ All new types under the rest package in iceberg-core

   • Everything sits under core/src/main/java/org/apache/iceberg/rest/{events,requests,responses}/

Followed the parser patterns from your referenced commits (1cb88a6 and f19643a).

@c-thiel — tagging you as the proposal author; happy to incorporate any feedback on the operation-type modeling or event semantics.

[stevenzwu]

@visit2rahul I already opened a draft PR: #15990

We need to address some spec discussions first

[visit2rahul]

Thanks for the heads-up @stevenzwu — didn't see the draft PR. Happy to close this in favor of #15990, or if there are parts of this work that are useful I'm glad to help. Let me know how you'd like to proceed.