test: add test cases for real number columns

internal/endtoend/testdata/emit_pointers_for_null_types/mysql/sql/real_number.sql

@@ -0,0 +1,19 @@
+CREATE TABLE dt_real_number (
+	a double,
+  b double precision,
+  c real,
+  d float,
+  e decimal,
+  f dec,
+  g fixed
+);
+
+CREATE TABLE dt_real_number_not_null (
+  a double not null,
+  b double precision not null,
+  c real not null,
+  d float not null,
+  e decimal not null,
+  f dec not null,
+  g fixed not null
+);