Fix clippy warnings in the generated code

[fpoli]

The java_package! prucedural macro currently generates code on which clippy reports some warnings. For example:

$ cargo clippy --manifest-path=test-crates/Cargo.toml

warning: redundant field names in struct initialization
  --> viper/src/lib.rs:78:5
   |
78 |     class CarbonVerifier {
   |     ^^^^^ help: replace it with: `a0`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_field_names
   = note: `#[warn(clippy::redundant_field_names)]` on by default

warning: redundant field names in struct initialization
  --> viper/src/lib.rs:78:5
   |
78 |     class CarbonVerifier {
   |     ^^^^^ help: replace it with: `a1`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_field_names

warning: redundant field names in struct initialization
  --> viper/src/lib.rs:46:5
   |
46 |     class Program {
   |     ^^^^^ help: replace it with: `a0`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_field_names

(...)

warning: this function has too many arguments (9/7)
  --> viper/src/lib.rs:46:5
   |
46 |     class Program {
   |     ^^^^^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#too_many_arguments
   = note: `#[warn(clippy::too_many_arguments)]` on by default

warning: `viper` (lib) generated 12 warnings

In general, it would be nice to fix or suppress these, so that users of the macro don't get warnings for Rust code which they didn't write.

The last clippy::too_many_arguments warning, in particular, correctly signals that a Java method has too many arguments. However, reporting it in the Rust crate that uses the method is incorrect. It should be responsibility of a Java linter (if one is used) to report the warning on the Java codebase.