Update to Current Nightly Version

[ThePoultryMan]

Changes

Non-Rust

• Update R8 to 8.11.18 (from 8.9.35)
• Source code was formatted with cargo fmt

Rust Changes

• Updated to current nightly (at the time of writing), which is rust version 1.91-nightly.
• Added trait for converting implemented items to Idents with TyCtxt.
  • This stems from the change, introduced Retire hir::*ItemRef. rust-lang/rust#143357, which replaces *ItemRef with *ItemId. So we have to get the AssocItem from the function TyCtxt::associated_item, which we can the get the Ident from.
  • Currently only implemented for ImplItemId and TraitItemId.
• Java home is first attempted to be located using java-locator, if that fails, it then uses "JAVA_HOME".

Breaks

• The just_main_fn test. I don't know why, but I am looking into it.

[ThePoultryMan]

just_main_fn test doesn't work because it is trying to compile to the jvm-unknown-unknown target. That doesn't work because it can't get std.

[IntegralPilot]

Thank you so much @ThePoultryMan for all your effort in making this PR - it really means so much to me and it's super exciting that this is becoming an OSS project others contribute too!

Re the failing test:

• just_main_func testing using the custom target is intentional, the purpose of that test is to check if building is possible using the custom JSON target spec.
• The error is not related to being unable to get std, which is currently the intended behaviour with the custom target as we don't support enough of Rust (namely generics) to support compiling core or std for a custom target in their entirety (thus in all the other tests with don't use a custom target and piggyback off the host target)
• just_main_func uses a no_std, no_core environment to get around this the limitation of being unable to use the core or std libraries when compiling for the custom target.
• This failure is instead related to a recent change in the JSON spec for rustc target files.
• jvm-unknown-unknown.json.template just needs a minor change to fix this - target-pointer-width needs to be changed to the integer 32 rather than the current string "32".

If you could please make this adjustment in the PR then we can merge it and fully support the latest nightly! Thank you so much again for all your effort! :)

[IntegralPilot]

Actually, I'll just merge this and then push the manual update to jvm-unknown-unknown.json.template needed to get just_main_func to pass to main (there's also a removal of an enum variant that came out with the latest nightly a few minutes ago, rust-lang/rust#146564, that needs a small change to fix that I'll handle). Thank you SO MUCH again for your amazing work! :)