feat: optional args are now specified separately from required args

BREAKING CHANGE: optional arguments are no longer allowed to be specified
as a part of FunctionArgument messages.  Instead they are now specified
separately as part of the function invocation.

BREAKING CHANGE: optional arguments are now specified separately from
required arguments in the YAML specification.

Co-authored-by: Benjamin Kietzman <[email protected]>

extensions/functions_aggregate_approx.yaml

@@ -2,7 +2,7 @@
 ---
 aggregate_functions:
   - name: "approx_count_distinct"
-    description:  >-
+    description: >-
       Calculates the approximate number of rows that contain distinct values of the expression argument using
       HyperLogLog. This function provides an alternative to the COUNT (DISTINCT expression) function, which
       returns the exact number of rows that contain distinct values of an expression. APPROX_COUNT_DISTINCT

extensions/functions_aggregate_generic.yaml

@@ -5,22 +5,21 @@ aggregate_functions:
     description: Count a set of values
     impls:
       - args:
-          - name: overflow
-            options: [SILENT, SATURATE, ERROR]
-            required: false
           - name: x
             value: any
+        options:
+          overflow:
+            values: [SILENT, SATURATE, ERROR]
         nullability: DECLARED_OUTPUT
         decomposable: MANY
         intermediate: i64
         return: i64
   - name: "count"
     description: "Count a set of records (not field referenced)"
     impls:
-      - args:
-          - name: overflow
-            options: [SILENT, SATURATE, ERROR]
-            required: false
+      - options:
+          overflow:
+            values: [SILENT, SATURATE, ERROR]
         nullability: DECLARED_OUTPUT
         decomposable: MANY
         intermediate: i64