Try to improve rust code readability

[Lol3rrr]

As suggested in issue #218

Type of changes

• Try to flatten code by using early returns/continues if there is only a single happy path in a function or loop
• Change repetitive matches with map_err
• Change matches returning true/false with matches! macro

[Lol3rrr]

I was also thinking about replacing the use of lazy_static with the new LazyLock or similar features in the standard library to remove the dependency, but I was not sure about the supported/used compiler versions

[LaihoE]

Looks good! Sure we can replace lazy_static also but maybe make it a separate pr.

[LaihoE]

As for the compiler version, It would be good to set the version in the Cargo.toml as protobuf often also has issues with some versions.

[Lol3rrr]

I think this is most of the easy to spot things, there are some other parts that seem more complicated and I don't think this would be the right place to change them.

I will open another PR for removing lazy_static and maybe another one to see what clippy would suggest

[LaihoE]

This contains quite a lot of code already, are you ready to merge this? you can always open a new pr with more refactors.

[Lol3rrr]

Yeah I would be ready, in my previous comment I meant that there are potentially more things to do, but they would be in different PRs, sorry if that was not clear.