resources: Fix 2 image file cache key issues

* Always include the content hash in the cache key for unprocessed images.
* Always include the image config hash in the cache key.

This is also a major cleanup/simplification of the implementation in this area.

Note that this, unfortunately, forces new hashes/filenames for generated images.

Fixes #13273
Fixes #13272

config/namespace.go

@@ -22,7 +22,7 @@ import (
 func DecodeNamespace[S, C any](configSource any, buildConfig func(any) (C, any, error)) (*ConfigNamespace[S, C], error) {
 	// Calculate the hash of the input (not including any defaults applied later).
 	// This allows us to introduce new config options without breaking the hash.
-	h := hashing.HashString(configSource)
+	h := hashing.HashStringHex(configSource)
 
 	// Build the config
 	c, ext, err := buildConfig(configSource)

config/namespace_test.go

@@ -43,7 +43,7 @@ func TestNamespace(t *testing.T) {
 	c.Assert(err, qt.IsNil)
 	c.Assert(ns, qt.Not(qt.IsNil))
 	c.Assert(ns.SourceStructure, qt.DeepEquals, map[string]interface{}{"foo": "bar"})
-	c.Assert(ns.SourceHash, qt.Equals, "1450430416588600409")
+	c.Assert(ns.SourceHash, qt.Equals, "1420f6c7782f7459")
 	c.Assert(ns.Config, qt.DeepEquals, &tstNsExt{Foo: "bar"})
 	c.Assert(ns.Signature(), qt.DeepEquals, []*tstNsExt(nil))
 }