test(script): Update from rustc's test suite (#16169)

### What does this PR try to resolve?

Update to rust-lang/rust@bc1d727

### How to test and review this PR?

See
<https://github.com/rust-lang/cargo/blob/master/tests/testsuite/script/rustc_fixtures/README.md>

Author: weihanglo

tests/testsuite/script/rustc.rs

@@ -0,0 +1,4 @@
+---
+-
+---
+1

tests/testsuite/script/rustc_fixtures/auxiliary/expr.rs

@@ -1,8 +1,20 @@
 extern crate proc_macro;
-use proc_macro::TokenStream;
+use proc_macro::{Literal, TokenStream};
 
 #[proc_macro]
 pub fn check(_: TokenStream) -> TokenStream {
+    // In the following test cases, the `---` may look like the start of frontmatter but it is not!
+    // That's because it would be backward incompatible to interpret them as such in the latest
+    // stable edition. That's not only the case due to the feature gate error but also due to the
+    // fact that we "eagerly" emit errors on malformed frontmatter.
+
+    // issue: <https://github.com/rust-lang/rust/issues/145520>
+    _ = "---".parse::<TokenStream>();
+    // Just a sequence of regular Rust punctuation tokens.
     assert_eq!(6, "---\n---".parse::<TokenStream>().unwrap().into_iter().count());
+
+    // issue: <https://github.com/rust-lang/rust/issues/146132>
+    assert!("---".parse::<Literal>().is_err());
+
     Default::default()
 }

tests/testsuite/script/rustc_fixtures/auxiliary/makro.rs

@@ -2,7 +2,7 @@
 ---cargo
 # Beware editing: it has numerous whitespace characters which are important.
 # It contains one ranges from the 'PATTERN_WHITE_SPACE' property outlined in
-# https: //unicode.org/Public/UNIDATA/PropList.txt
+# https://unicode.org/Public/UNIDATA/PropList.txt
 #
 # The characters in the first expression of the assertion can be generated
 # from: "4\u{0C}+\n\t\r7\t*\u{20}2\u{85}/\u{200E}3\u{200F}*\u{2028}2\u{2029}"

tests/testsuite/script/rustc_fixtures/frontmatter-contains-whitespace.rs renamed to tests/testsuite/script/rustc_fixtures/content-contains-whitespace.rs

@@ -1,4 +1,4 @@
----cargo
+--- cargo
 package.description = """
 🏳️‍⚧️
 """

tests/testsuite/script/rustc_fixtures/frontmatter-contains-whitespace.stderr renamed to tests/testsuite/script/rustc_fixtures/content-contains-whitespace.stderr

@@ -4,7 +4,6 @@ package.description = """
 ---
 
 """
-
 ----
 
 //@ check-pass