simplify plurals in fluent messages using hir::ConstContext

compiler/rustc_error_messages/locales/en-US/const_eval.ftl

@@ -7,11 +7,7 @@ const-eval-thread-local-access =
     thread-local statics cannot be accessed at compile-time
 
 const-eval-static-access =
-    { $kind -> 
-        [constant function] constant functions
-        [static] statics
-        *[constant] constants
-    } cannot refer to statics
+    {$kind}s cannot refer to statics
     .help = consider extracting the value of the `static` to a `const`, and referring to that
     .teach-note = `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
     .teach-help = To fix this, the value can be extracted to a `const` and then used.
@@ -28,20 +24,8 @@ const-eval-raw-ptr-comparison =
 const-eval-panic-non-str = argument to `panic!()` in a const context must have type `&str`
 
 const-eval-mut-deref =
-    mutation through a reference is not allowed in { $kind -> 
-        [constant function] constant functions
-        [static] statics
-        *[constant] constants
-    }
-
-const-eval-transient-mut-borrow = mutable references are not allowed in { $kind -> 
-        [constant function] constant functions
-        [static] statics
-        *[constant] constants
-    }
-
-const-eval-transient-mut-borrow-raw = raw mutable references are not allowed in { $kind -> 
-        [constant function] constant functions
-        [static] statics
-        *[constant] constants
-    }
+    mutation through a reference is not allowed in {$kind}s
+
+const-eval-transient-mut-borrow = mutable references are not allowed in {$kind}s
+
+const-eval-transient-mut-borrow-raw = raw mutable references are not allowed in {$kind}s