Complete enum variants identically to structures.

In particular:
 - unit variants now display in the menu as "Variant", complete to "Variant", and display a detail of "Variant" (was "()")
 - tuple variants now display in the menu as "Variant(…)", complete to "Variant(${1:()})$0" (was "Variant($0)"), and display a detail of "Variant(type)" (was "(type)")
 - record variants now display in the menu as "Variant {…}", complete to "Variant { x: ${1:()} }$0" (was "Variant"), and display a detail of "Variant { x: type }" (was "{x: type}")

This behavior is identical to that of struct completions. In addition, tuple variants no longer set triggers_call_info, as to my understanding it's unnecessary now that we're emitting placeholders.

Tests have been updated to match, and the render::enum_variant::tests::inserts_parens_for_tuple_enums test has been removed entirely as it's covered by other tests (render::enum_detail_includes_{record, tuple}_fields, render::enum_detail_just_name_for_unit, render::pattern::enum_qualified).

crates/ide_completion/src/tests/expression.rs

@@ -61,7 +61,7 @@ fn baz() {
             fn function()    fn()
             sc STATIC
             un Union
-            ev TupleV(…)     (u32)
+            ev TupleV(…)     TupleV(u32)
             ct CONST
         "#]],
     )
@@ -171,7 +171,7 @@ impl Unit {
             fn function()   fn()
             sc STATIC
             un Union
-            ev TupleV(…)    (u32)
+            ev TupleV(…)    TupleV(u32)
             ct CONST
         "#]],
     );
@@ -200,7 +200,7 @@ impl Unit {
             fn function() fn()
             sc STATIC
             un Union
-            ev TupleV(…)  (u32)
+            ev TupleV(…)  TupleV(u32)
             ct CONST
         "#]],
     );
@@ -543,9 +543,9 @@ fn func() {
 }
 "#,
         expect![[r#"
-            ev TupleV(…)   (u32)
-            ev RecordV     {field: u32}
-            ev UnitV       ()
+            ev TupleV(…)   TupleV(u32)
+            ev RecordV {…} RecordV { field: u32 }
+            ev UnitV       UnitV
             ct ASSOC_CONST const ASSOC_CONST: ()
             fn assoc_fn()  fn()
             ta AssocType   type AssocType = ()

crates/ide_completion/src/tests/pattern.rs

@@ -218,7 +218,7 @@ fn foo() {
         expect![[r#"
             kw ref
             kw mut
-            ev E::X  ()
+            ev E::X  E::X
             en E
             ma m!(…) macro_rules! m
         "#]],
@@ -291,9 +291,9 @@ fn func() {
 }
 "#,
         expect![[r#"
-            ev TupleV(…) (u32)
-            ev RecordV   {field: u32}
-            ev UnitV     ()
+            ev TupleV(…)   TupleV(u32)
+            ev RecordV {…} RecordV { field: u32 }
+            ev UnitV       UnitV
         "#]],
     );
 }

crates/ide_completion/src/tests/use_tree.rs

@@ -167,7 +167,7 @@ impl Foo {
 }
 "#,
         expect![[r#"
-            ev Variant ()
+            ev Variant Variant
         "#]],
     );
 }