Rollup merge of #70918 - tobithiel:fix_forbid_override, r=davidtwco

rustc_session: forbid lints override regardless of position

Addresses the regression reported in #70819 for command line arguments, but does not address the source code flag regression.

src/test/ui-fulldeps/lint-group-forbid-always-trumps-cli.rs

@@ -0,0 +1,7 @@
+// aux-build:lint-group-plugin-test.rs
+// compile-flags: -F unused -A unused
+
+fn main() {
+    let x = 1;
+    //~^ ERROR unused variable: `x`
+}

src/test/ui-fulldeps/lint-group-forbid-always-trumps-cli.stderr

@@ -0,0 +1,10 @@
+error: unused variable: `x`
+  --> $DIR/lint-group-forbid-always-trumps-cli.rs:5:9
+   |
+LL |     let x = 1;
+   |         ^ help: if this is intentional, prefix it with an underscore: `_x`
+   |
+   = note: `-F unused-variables` implied by `-F unused`
+
+error: aborting due to previous error
+