Lazily invoke findLibrary to avoid UnsatisfiedLinkError when service loaded SymbolLookup successfuly found library

[victorgveloso]

FIX #81
The problem in ChainedLibraryLookup.get comes from the fact findLibrary is invoked eagerly, thus leading to UnsatisfiedLinkError even when SymbolLookup never requires using the SymbolLookup returned by findLibrary. Actually, the solution is quite simple and it's inspired by the initialization of the lookup local variable.

It leverages the fact SymbolLookup is a FunctionalInterface to implement it in Lazily manner. All you need to do is replace the following line:

return lookup.or(findLibrary(arena)).or(Linker.nativeLinker().defaultLookup());

With the following line

return lookup.or((name) -> findLibrary(arena).find(name)).or(Linker.nativeLinker().defaultLookup());

Notice that now findLibrary will only execute if all SymbolLookup loaded by ServiceLoader failed to lookup the library.

[victorgveloso]

This PR only applies a simple trick to fix custom library loading when the library is not in java.library.path but a service loaded SymbolLookup successfully found it.

[victorgveloso]

Please, @ObserverOfTime , consider accepting this bugfix otherwise jtreesitter service loader in LibraryLoader is useless (as ChainedLibraryLoader throws exceptions when the native library is not found in java.library.path even before trying to run any custom LibraryLoader)

[ObserverOfTime]

I'll incorporate it in #128.

[victorgveloso]

I changed back the base branch to improve-exceptions so that you can easily integrate it while giving the proper credits for my contribution. You can accept this PR now and it won't affect the master branch