improve error message for unexpected comma token in multiline block

confusing diagnostics, issue #72253

add test for confusing error message, issue-72253


remove is_multiline check, refactor to self.expect(&token:Semi)


update issue-72253 tests


return Ok

src/test/ui/issues/issue-72253.rs

@@ -0,0 +1,6 @@
+fn main() {
+    let a = std::process::Command::new("echo")
+        .arg("1")
+        ,arg("2") //~ ERROR expected one of `.`, `;`, `?`, or an operator, found `,`
+        .output();
+}

src/test/ui/issues/issue-72253.stderr

@@ -0,0 +1,10 @@
+error: expected one of `.`, `;`, `?`, or an operator, found `,`
+  --> $DIR/issue-72253.rs:4:9
+   |
+LL |         .arg("1")
+   |                  - expected one of `.`, `;`, `?`, or an operator
+LL |         ,arg("2")
+   |         ^ unexpected token
+
+error: aborting due to previous error
+