tests: logging/dictionary: limit allowed platforms

Instead of using filter (which is expensive in terms of CI as
it needs to run cmake on everything to get the full kconfigs
before filtering can be done), change that to a curated list
of allowed platforms. This avoids the expensive filtering
operation, yet can still run on some emulated platforms to
verify the dictionary output.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

tests/subsys/logging/dictionary/testcase.yaml

@@ -1,14 +1,20 @@
 common:
   # For twister runs, only logging backends with in hexidecimal format
   # are supported. Currently, only UART logging backend does that.
-  filter: CONFIG_LOG_BACKEND_UART and CONFIG_LOG_BACKEND_UART_OUTPUT_DICTIONARY
+  # So platform_allow list needs to limit to those platforms.
-          and CONFIG_LOG_BACKEND_UART_OUTPUT_DICTIONARY_HEX
+  platform_allow:
+    - mps2/an385
+    - qemu_cortex_a53
+    - qemu_riscv32
+    - qemu_riscv64
+    - qemu_x86
+    - qemu_x86_64
+  integration_platforms:
+    - qemu_x86
+    - qemu_x86_64
 tests:
   logging.dictionary:
     tags: logging
-    integration_platforms:
-      - qemu_x86
-      - qemu_x86_64
     harness: pytest
     harness_config:
       pytest_root:
@@ -24,6 +30,3 @@ tests:
         - "pytest/test_logging_dictionary.py"
       pytest_args:
         - "--fpu"
-    integration_platforms:
-      - qemu_x86
-      - qemu_x86_64