pytest sample & docs: Replace native_posix with native_sim

In the docs replace references to native_posix with native_sim
Switch the default test platform to native_sim from native_posix

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

samples/subsys/testsuite/pytest/basic/testcase.yaml

@@ -1,6 +1,8 @@
 tests:
   sample.twister.pytest:
-    platform_allow: native_posix
+    platform_allow:
+      - native_posix
+      - native_sim
     harness: pytest
     harness_config:
       pytest_args: ["--custom-pytest-arg", "foo", "--cmdopt", "."]
@@ -8,4 +10,4 @@ tests:
       - test_framework
       - pytest
     integration_platforms:
-      - native_posix
+      - native_sim

samples/subsys/testsuite/pytest/shell/testcase.yaml

@@ -6,7 +6,7 @@ tests:
     extra_configs:
       - arch:posix:CONFIG_NATIVE_UART_0_ON_STDINOUT=y
     integration_platforms:
-      - native_posix
+      - native_sim
       - qemu_cortex_m3
     tags:
       - test_framework

scripts/pylib/pytest-twister-harness/README.rst

@@ -20,8 +20,8 @@ Run exemplary test shell application by Twister:
 
   cd ${ZEPHYR_BASE}
 
-  # native_posix & QEMU
-  ./scripts/twister -p native_posix -p qemu_x86 -T samples/subsys/testsuite/pytest/shell
+  # native_sim & QEMU
+  ./scripts/twister -p native_sim -p qemu_x86 -T samples/subsys/testsuite/pytest/shell
 
   # hardware
   ./scripts/twister -p nrf52840dk_nrf52840 --device-testing --device-serial /dev/ttyACM0 -T samples/subsys/testsuite/pytest/shell
@@ -34,8 +34,8 @@ or build shell application by west and call pytest directly:
 
   cd ${ZEPHYR_BASE}/samples/subsys/testsuite/pytest/shell
 
-  # native_posix
-  west build -p -b native_posix -- -DCONFIG_NATIVE_UART_0_ON_STDINOUT=y
+  # native_sim
+  west build -p -b native_sim -- -DCONFIG_NATIVE_UART_0_ON_STDINOUT=y
   pytest --twister-harness --device-type=native --build-dir=build -p twister_harness.plugin
 
   # QEMU