Remove Java dependency

[valentjn]

GraalVM is a possibility to compile Java programs to bytecode; the resulting executables don't need a JVM anymore. This would eliminate the need to install Java to use LT_EX. However, I see some challenges:

• The language extensions also have Java code in them and would have to be compiled to shared libraries.
• The binaries would be platform-dependent. Currently, I don't see a way to have different *.vsixs for different platforms, so the preferable way seems to be downloading the platform-dependent parts on demand after installing the extension. We would still have to provide *.vsix files for offline installation.

[valentjn]

I have tried GraalVM, but it only supports a subset of all Java features, especially with respect to reflection.

I'm currently working on having LT_EX download Java on-demand if it cannot be found on the system (people will be able to override this with a setting). That's more or less equivalent to what's said in the description above. There will be an option to download an offline version of LT_EX that already contains Java.

[valentjn]

I deem this as fixed with the upcoming LT_EX 5.x as shipping JARs together with a JRE is basically the same as shipping binaries, from a user perspective.

[valentjn]

Fix released in 5.0.0.