Update `replace_consts` lint wrt. stabilized `assoc_int_consts` feature

[phansch]

rust-lang/rust#68952 stabilized the assoc_int_consts feature for Rust 1.34. For Clippy this is relevant for at least the replace_consts lint:

As far as I can tell, that lint was meant to suggest to use the associated methods on the integer primitives, instead of the constants that have now been soft-deprecated in rust-lang/rust#68952. Although, the lint doesn't really provide a reason why one is better over the other. (Please correct me if I misunderstood that lint)

The RFC also mentions a deprecation of the associated functions the lint is currently suggesting, so we might want to deprecate replace_consts and have a different lint that suggests the associated constants instead of the associated methods 🔄

[phansch]

Oh, I just found #2380 after the fact, so I'm going to close this issue and continue in #2380