Sort-indirect PR broken into smaller parts: part 2/6 - fix the Sort part of ListOptions (#611)

* Move types related to list options and sql queries into their own package.

The problem having these in the informer package is that eventually code
in other packages will need to import `informer` only for constants or types,
but some members of the informer package may already depend on those. Best to
move type definitions into their own simpler package.

* Fix the ListOptions sort field.

Instead of making it a single array-ish field, convert it into a
true array of Sort Directives.  Easier to read, less bending backwards.

* Rebasing (or human error) duplicated 'NewSortList'.

pkg/sqlcache/sqltypes/types.go

@@ -28,7 +28,7 @@ type ListOptions struct {
 	ChunkSize  int
 	Resume     string
 	Filters    []OrFilter
-	Sort       Sort
+	SortList   SortList
 	Pagination Pagination
 }
 
@@ -57,8 +57,8 @@ type OrFilter struct {
 // The order is represented by prefixing the sort key by '-', e.g. sort=-metadata.name.
 // e.g. To sort internal clusters first followed by clusters in alpha order: sort=-spec.internal,spec.displayName
 type Sort struct {
-	Fields [][]string
-	Orders []SortOrder
+	Fields []string
+	Order  SortOrder
 }
 
 type SortList struct {