say: move the copy deck into a package memory can import (V-506)

The summaries family is spoken by internal/memory, internal/morning and
internal/tasks. internal/phraser already imports internal/memory, so the
deck cannot stay in phraser without a cycle.

internal/say is a leaf: embed, json, math/rand, strings, sync. The four
phraser families keep their files and their floors and now call say.Load,
*say.Deck, Text, Matches, Variants, RequirePlaceholder and RegisterFloor.
No copy changed and no behaviour changed.

internal/phraser/failure_test.go

@@ -13,7 +13,7 @@ import (
 // fallbacks_ru_v1.json break Go tests, which is the coupling this file removed.
 func isFallback(t *testing.T, key, sources, got string) bool {
 	t.Helper()
-	return DefaultFallbacks().deck().matches(key, map[string]string{"sources": sources}, got)
+	return DefaultFallbacks().deck().Matches(key, map[string]string{"sources": sources}, got)
 }
 
 // A dead server must be distinguishable from bad phrasing. Both PhraseChat and