userspace tests/samples: Exclude in posix arch

These samples & tests cannot be run in this architecture
as it does not support userspace.
Today they are filtered by kconfig, which works but spends
time running cmake.
As native_posix is a default test platform it is better
to filter it alltogether by arch, which saves quite a lot
of time.

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

samples/userspace/hello_world_user/sample.yaml

@@ -14,4 +14,6 @@ common:
 tests:
   sample.helloworld:
     filter: CONFIG_ARCH_HAS_USERSPACE
+    arch_exclude:
+      - posix
     tags: introduction

samples/userspace/prod_consumer/sample.yaml

@@ -13,3 +13,5 @@ common:
 tests:
   sample.userspace.prod_consumer:
     filter: CONFIG_ARCH_HAS_USERSPACE
+    arch_exclude:
+      - posix

samples/userspace/shared_mem/sample.yaml

@@ -14,6 +14,8 @@ common:
 tests:
   sample.kernel.memory_protection.shared_mem:
     filter: CONFIG_ARCH_HAS_USERSPACE
+    arch_exclude:
+      - posix
     platform_exclude:
       - twr_ke18f
       - cy8cproto_062_4343w

tests/benchmarks/sched_userspace/testcase.yaml

@@ -7,6 +7,8 @@ tests:
       - userspace
     slow: true
     filter: CONFIG_ARCH_HAS_USERSPACE
+    arch_exclude:
+      - posix
     harness: console
     harness_config:
       type: multi_line