Add missing static constructors to ResponseEntity

[KarboniteKream]

Motivation:

This PR adds more static constructors to ResponseEntity to match those available in the deprecated HttpResult.

Modifications:

• Add static constructors for HttpStatus
• Replace Void return type with <T> (breaking change)
• Add missing tests to rxjava3 module

Result:

• ResponseEntity can now be used the same way that HttpResult was used.

[github-actions]

🔍 Build Scan® (commit: 0e51aee)

Job name	Status	Build Scan®
build-ubicloud-standard-8-jdk-8	✅	https://ge.armeria.dev/s/5wiigfqpy5i2g
build-ubicloud-standard-8-jdk-21-snapshot-blockhound	✅	https://ge.armeria.dev/s/r4umtongfflk4
build-ubicloud-standard-8-jdk-17-min-java-17-coverage	✅	https://ge.armeria.dev/s/m5de2zj63gxxu
build-ubicloud-standard-8-jdk-17-min-java-11	❌ (failure)	https://ge.armeria.dev/s/pg6rj6j25au5s
build-ubicloud-standard-8-jdk-17-leak	✅	https://ge.armeria.dev/s/cecscki5neyxa
build-ubicloud-standard-8-jdk-11	✅	https://ge.armeria.dev/s/cuzw2beixipmq
build-macos-12-jdk-21	✅	https://ge.armeria.dev/s/kzlimnieqmqdc

[minwoox]

Looks great! Thanks! 😆

[jrhee17]

👍 👍

[ikhoon]

Thanks!