[Feature]: Automatically install SDKs

1. Your usage scenarios?

I cd in a directory and I expect the JDK to be available.

2. What is your expected outcome?

vfox asking for JDK installation if not installed yet.

Examples that sdk is set if installed:

• /tmp/x: 21
• /tmp/y: 20
• /c/git-repositories/jabref-all/javafxreproducer: last SDK, because 22 was not installed before.

$ cat /c/TEMP/x/.tool-versions
java 21.0.2+13

koppor@DESKTOP-KAK953S MINGW64 /c/TEMP/x (master)
$ java -version
openjdk version "21.0.2" 2024-01-16
OpenJDK Runtime Environment (build 21.0.2+13-58)
OpenJDK 64-Bit Server VM (build 21.0.2+13-58, mixed mode, sharing)

$ cat /c/TEMP/y/.tool-versions
java 20.0.2+9

koppor@DESKTOP-KAK953S MINGW64 /c/TEMP/y
$ java -version
openjdk version "20.0.2" 2023-07-18
OpenJDK Runtime Environment (build 20.0.2+9-78)
OpenJDK 64-Bit Server VM (build 20.0.2+9-78, mixed mode, sharing)

koppor@DESKTOP-KAK953S MINGW64 /c/git-repositories/jabref-all/javafxreproducer (add-textfield-mwe)
$ cat .tool-versions
java 22.0.1+8-tem

koppor@DESKTOP-KAK953S MINGW64 /c/git-repositories/jabref-all/javafxreproducer (add-textfield-mwe)
$ java -version
openjdk version "20.0.2" 2023-07-18
OpenJDK Runtime Environment (build 20.0.2+9-78)
OpenJDK 64-Bit Server VM (build 20.0.2+9-78, mixed mode, sharing)

Reproduce the directory-change scenarios from the issue and trace vfox's version resolution and SDK installation flow, including the Java SDK plugin. Define how a missing version should trigger installation and how the existing fallback behavior should work, then add coverage for the listed project-directory cases.