FFI `ICU4X` prefix

[robertbastian]

All our diplomat types are prefixed with ICU4X. This is probably due to C not having namespacing. However, in other languages, this is not idiomatic. Could a prefix be added as part of Diplomat's C generation instead?

[sffc]

Duplicate of https://github.com/unicode-org/icu4x/issues/2182

[robertbastian]

Isn't https://github.com/unicode-org/icu4x/issues/2182 much wider in scope, i.e. proper C++ namespacing? I'm thinking of removing the prefix from all names, and just slapping it on every name that is generated for C and C++ (but not for say Dart).

[sffc]

I think we had discussed that in the context of #2182 but there was some reason it was hard to do. @Manishearth ?

[sffc]

Action: @Manishearth to open or track a Diplomat issue.

[Manishearth]

https://github.com/rust-diplomat/diplomat/issues/103

[robertbastian]

https://github.com/rust-diplomat/diplomat/pull/416 adds HIR support for custom ABI renames.

[Manishearth]

https://github.com/rust-diplomat/diplomat/issues/422 is the issue that would let us make this change today . It is a bit more annoying to implement.

[robertbastian]

Fixed by #5228