Fix unknown-crate when using self-profile with rustdoc

... by removing a duplicate `crate_name` field in `interface::Config`,
making it clear that rustdoc should be passing it to `config::Options`
instead.

src/test/run-make-fulldeps/issue-19371/foo.rs

@@ -56,7 +56,6 @@ fn compile(code: String, output: PathBuf, sysroot: PathBuf) {
         file_loader: None,
         diagnostic_output: DiagnosticOutput::Default,
         stderr: None,
-        crate_name: None,
         lint_caps: Default::default(),
         register_lints: None,
         override_queries: None,