tests/kernel/*: Switch integration platform to native_sim

Swith integration_platforms from native_posix(_64)
to native_sim(_64).
And replace it also in a comment.

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

tests/kernel/common/testcase.yaml

@@ -20,7 +20,7 @@ tests:
     # Some configurations are known-incompliant and won't build
     filter: not ((CONFIG_I2C or CONFIG_SPI) and CONFIG_USERSPACE)
     integration_platforms:
-      - native_posix
+      - native_sim
     extra_configs:
       - CONFIG_MISRA_SANE=y
   kernel.common.minimallibc:

tests/kernel/device/testcase.yaml

@@ -3,7 +3,7 @@ common:
     - device
     - userspace
   integration_platforms:
-    - native_posix
+    - native_sim
 tests:
   kernel.device:
     tags:

tests/kernel/timer/cycle64/testcase.yaml

@@ -1,6 +1,6 @@
 # Note: Re: slow vs fast
 #
-# Some platforms such as native_posix, qemu_riscv32, qemu_riscv64
+# Some platforms such as native_sim, qemu_riscv32, qemu_riscv64
 # complete these tests almost instantaneously because of qemu timer
 # quirks ("time warp") even though the test reports that it completes
 # in e.g. 14 s. We can take advantage of that for fast tests on each PR