Upgrade to Spring Boot 4

[steven-sheehy]

Problem

As a developer, we'd like to use the latest Spring Boot version to take advantage of performance optimizations and bug fixes.

Solution

• Depends on grpc-spring-boot-starter not compatible with Spring Boot 4 #12452
• Bump spring boot to 4
• Use jackson2 bridge library to avoid jackson3 conversion
• Fix any issues

Alternatives

No response