Add tests that show the sum() functions aren't polymorphic yet

internal/endtoend/testdata/func_match_types/mysql/query.sql

@@ -1,4 +1,4 @@
 -- name: AuthorPages :many
-select author, count(title) as num_books, SUM(pages) as total_pages
+select author, count(title) as num_books, SUM(pages) as total_pages, SUM(score) AS sum_score, SUM(price) AS sum_price, SUM(avg_word_length) as sum_avg_length
 from books
 group by author;

internal/endtoend/testdata/func_match_types/mysql/schema.sql

@@ -2,5 +2,8 @@ CREATE TABLE books (
                        id   integer PRIMARY KEY,
                        title text      NOT NULL,
                        author text     NOT NULL,
-                       pages integer      NOT NULL
+                       pages integer   NOT NULL,
+                       score float     NOT NULL,
+                       price decimal(4, 2) NOT NULL,
+                       avg_word_length double NOT NULL
 );

internal/endtoend/testdata/func_match_types/postgresql/query.sql

@@ -1,4 +1,4 @@
 -- name: AuthorPages :many
-select author, count(title) as num_books, SUM(pages) as total_pages
+select author, count(title) as num_books, SUM(pages) as total_pages, SUM(score) AS sum_score, SUM(price) AS sum_price, SUM(avg_word_length) as sum_avg_length
 from books
 group by author;

internal/endtoend/testdata/func_match_types/postgresql/schema.sql

@@ -2,5 +2,8 @@ CREATE TABLE books (
   id     integer PRIMARY KEY,
   title  text    NOT NULL,
   author text    NOT NULL,
-  pages  integer NOT NULL
+  pages  integer NOT NULL,
+  score float    NOT NULL,
+  price DECIMAL(4, 2) NOT NULL,
+  avg_word_length DOUBLE NOT NULL
 );