Use SELF for Builder Self Type Parameter

[minwoox]

Motivation:
See #5684 for the motivation.

Modifications:

• Refactored builder classes to use the SELF type parameter for the builder's self-referencing methods.
  • Didn't refactor builder classes if their parent classes are public due to breaking changes. Will revisit this later if making changes is acceptable.

Result:

• Reduced the need for cumbersome and error-prone method overrides.

[github-actions]

🔍 Build Scan® (commit: 2a1fa23)

Job name	Status	Build Scan®
build-windows-latest-jdk-21	✅	https://ge.armeria.dev/s/faunpx6pzobgi
build-self-hosted-unsafe-jdk-8	✅	https://ge.armeria.dev/s/34vebmf5oidri
build-self-hosted-unsafe-jdk-21-snapshot-blockhound	✅	https://ge.armeria.dev/s/vwk5saa2crwpq
build-self-hosted-unsafe-jdk-17-min-java-17-coverage	✅	https://ge.armeria.dev/s/7itnlfec2ahwi
build-self-hosted-unsafe-jdk-17-min-java-11	❌ (failure)	https://ge.armeria.dev/s/b22nrpw2hepu6
build-self-hosted-unsafe-jdk-17-leak	✅	https://ge.armeria.dev/s/njspoked6rdz4
build-self-hosted-unsafe-jdk-11	✅	https://ge.armeria.dev/s/4kpfthde3ie7m
build-macos-12-jdk-21	✅	https://ge.armeria.dev/s/ib3wpxkd6ewya

[jrhee17]

I'm all for making the implementation simpler 👍 If there are any issues (e.g. javadoc), I'd rather they be handled directly rather than us adding thousands of lines of code to avoid the issue.

[minwoox]

Resolving the conflicts is done. Meanwhile, I found other classes that I can also fix.
The superclasses of those classes are public but they are annotated with @UnstableApi.
Because this PR is already huge let me create a separate PR for the breaking.

[ikhoon]

Thanks! 👍👍