rustc_codegen_utils: revert some symbol_names refactors (while keeping the functional changes).
rustc_codegen_utils: revert some symbol_names refactors (while keeping the functional changes).

graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust