exo: Add exosphere.ini support and cal0 blanking

exosphere.ini will always be loaded and the values set by it.

User can still choose to override them with the `cal0blank` and `cal0writesys` in a boot entry.

Override keys get a 0 or 1.

bootloader/hos/hos.h

@@ -97,11 +97,11 @@ typedef struct _launch_ctxt_t
 	bool debugmode;
 	bool stock;
 	bool atmosphere;
-	bool exo_no_user_exceptions;
-	bool exo_user_pmu;
 	bool fss0_enable_experimental;
 	bool emummc_forced;
 
+	exo_ctxt_t exo_cfg;
+
 	ini_sec_t *cfg;
 } launch_ctxt_t;