Partial Application Syntax: Stage 1 (#9343)

* add partial application syntax and some tests

* remove unnecessary error message and hasPartial function from parseNewArguments

* add types for PartialExpression

* Update the tests

* rename PartialExpression to Partial

* move Partial from expressions to types and rename to ArgumentPlaceholder

* add tests for ArgumentPlaceholder in babel-generator

* rename Partial to ArgumentPlaceholder

* update the tests

* remove alias from the type and undo changes in generated folder

* adds a nice error message

* better definition for the type

* auto-generated files

* update the conditional for allowPlaceholder message and tests

* update CallExpression definition to accept ArgumentPlaceholder

* change description

* clean up

* indent ArgumentPlaceholder entry and revert unwanted changes

packages/babel-parser/ast/spec.md

@@ -72,6 +72,7 @@ These are the core @babel/parser (babylon) AST node types.
     - [LogicalExpression](#logicalexpression)
       - [LogicalOperator](#logicaloperator)
     - [SpreadElement](#spreadelement)
+    - [ArgumentPlaceholder](#argumentplaceholder)
     - [MemberExpression](#memberexpression)
     - [BindExpression](#bindexpression)
   - [ConditionalExpression](#conditionalexpression)
@@ -862,6 +863,14 @@ interface SpreadElement <: Node {
 }
 ```
 
+### ArgumentPlaceholder
+
+```js
+interface ArgumentPlaceholder <: Node {
+    type: "ArgumentPlaceholder";
+}
+```
+
 ### MemberExpression
 
 ```js