This allows dialect-specific attributes to be attached to func results. (or more specifically, FunctionLike ops).
For example:
```
func @f() -> (i32 {my_dialect.some_attr = 3})
```
This attaches my_dialect.some_attr with value 3 to the first result of func @f.
Another more complex example:
```
func @g() -> (i32, f32 {my_dialect.some_attr = "foo", other_dialect.some_other_attr = [1,2,3]}, i1)
```
Here, the second result has two attributes attached.
PiperOrigin-RevId: 275564165
Use OpInterfaces to add an interface for ops defining a return type function.
This change does not use this trait in any meaningful way, I'll use it in a
follow up to generalize and unify some of the op type traits/constraints. Also,
currently the infer type function can only be manually specified in C++, that should rather be the fallback in future.
PiperOrigin-RevId: 271883746
These two operation interfaces will be used in a followup to support building a callgraph:
* CallOpInterface
- Operations providing this interface are call-like, and have a "call" target. A call target may be a symbol reference, via SymbolRefAttr, or a SSA value.
* CallableOpInterface
- Operations providing this interfaces define destinations to call-like operations, e.g. FuncOp. These operations may define any number of callable regions.
PiperOrigin-RevId: 270723300
