Spring Apply "instanceof pattern matching" in the remainder of the code base

Overview

Since we began work on Spring Framework 6.0, we have taken several steps toward applying "instanceof pattern matching" in the code base.

I took a first pass using IDE tooling in Eclipse. Several external contributors have contributed ad hoc refactorings via PRs. And I have also contributed ad hoc refactorings as I encountered places in the code base where "instanceof pattern matching" could be applied.

However, there remain numerous places in the code base where this can been applied, and processing of ad hoc PRs is a bit laborious.

I have therefore opened this issue to "finish the job" in the remainder of the code base.

The "deliverables" track which modules have had "instanceof pattern matching" applied wherever feasible.

Deliverables

• [x] spring-aop
• [x] spring-aspects
• [x] spring-beans
• [x] spring-context
• [x] spring-context-indexer
• [x] spring-context-support
• [x] spring-core
• [x] spring-core-test
• [x] spring-expression
• [x] spring-instrument
• [x] spring-jcl
• [x] spring-jdbc
• [x] spring-jms
• [x] spring-messaging
• [x] spring-orm
• [x] spring-oxm
• [x] spring-r2dbc
• [x] spring-test
• [x] spring-tx
• [x] spring-web
• [x] spring-webflux
• [x] spring-webmvc
• [x] spring-websocket

Comment From: sbrannen

instanceof pattern matching has now been applied where feasible for src/main/java for every spring-* module.