refactor all attribute functions in rust-compile-base.cc

[saeitoshi-10]

gcc/rust/ChangeLog:
* backend/rust-compile-base.cc (get_attributes):removed checker function (get_trait_name):removed checker function
* util/rust-attributes.cc (Attributes::get_attributes):added checker function (Attributes::get_trait_name): added checker function
* util/rust-attributes.h: added functions definitions in the header file for access

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Addresses : #3291
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[powerboat9]

Are you trying to use those functions elsewhere in the codebase?

[saeitoshi-10]

no i didn't see any other implementations till but if it exists i'll be sure to replace that