all: generate json, not code

This includes modifying horsebot to use the generated JSON, as well as
moving the generator to another cmd/ directory.

Remove the generated code while we're here.
Koka tests still have to be updated, but it requires a JSON parser.

cmd/horsegen/sql/character.sql

@@ -0,0 +1,9 @@
+SELECT
+	"index" AS "id",
+	"text" AS "name",
+	ROW_NUMBER() OVER (ORDER BY "index") - 1 AS "index"
+FROM text_data
+WHERE category = 6 AND "index" BETWEEN 1000 AND 1999
+	-- Exclude characters who have no succession relations defined.
+	AND "index" IN (SELECT chara_id FROM succession_relation_member)
+ORDER BY "id"