Finish transition from semitransparent to semiopaque for rustc_macro_transparency

[Enselic]

Since it's a bit annoying to have different names for the same thing.

My understanding is that this is just internal stuff that is not part of any public API even tough rust-analyzer knows about it.

Continuation of #139084.

Discovered while investigating #150514.

Part of #150588.

[rustbot]

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

[rustbot]

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