tests/drivers/bbram: Switch to native_sim

Switch from native_posix to native_sim as default
test platform, switch overlays to native_sim.
For the HW test, filter whole posix arch to speed
up twister run.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

tests/drivers/bbram/emul/testcase.yaml

@@ -7,6 +7,6 @@ tests:
       - drivers
       - bbram
     harness: ztest
-    platform_allow: native_posix
+    platform_allow: native_sim
     integration_platforms:
-      - native_posix
+      - native_sim

tests/drivers/bbram/testcase.yaml

@@ -7,7 +7,7 @@ common:
     - bbram
   build_only: true
   harness: ztest
-  platform_exclude: native_posix
+  arch_exclude: posix
 tests:
   drivers.bbram.it8xxx2:
     filter: dt_compat_enabled("ite,it8xxx2-bbram")