suggest a float literal when dividing a floating-point type by {integer}

fix a message

implement a rustfix-applicable suggestion

implement `suggest_floating_point_literal`

add `ObligationCauseCode::BinOp`

remove duplicate code

fix function names in uitests

use `Diagnostic` instead of `DiagnosticBuilder`

compiler/rustc_middle/src/traits/mod.rs

@@ -368,6 +368,11 @@ pub enum ObligationCauseCode<'tcx> {
 
     /// From `match_impl`. The cause for us having to match an impl, and the DefId we are matching against.
     MatchImpl(ObligationCause<'tcx>, DefId),
+
+    BinOp {
+        rhs_span: Option<Span>,
+        is_lit: bool,
+    },
 }
 
 /// The 'location' at which we try to perform HIR-based wf checking.