tests: thread_analyzer: limit platforms to run on

This adds platform_allow to limit the scope of platforms to
build and run. This avoids the need to constantly nudge
the platform filter lists to exclude platforms which fail
to build or run due to incompatible kconfigs.

Fixes #76945

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

tests/subsys/debug/thread_analyzer/testcase.yaml

@@ -2,12 +2,18 @@ common:
   integration_platforms:
     - mps2/an385
     - qemu_x86_64
+  platform_allow:
+    # Representative platforms to make sure this builds without issues
+    # and the analyzer actually runs and outputs something.
+    - mps2/an385
+    - qemu_cortex_a53
+    - qemu_x86
+    - qemu_x86_64
+    - qemu_riscv32
+    - qemu_riscv64
   tags:
     - debug
     - thread_analyzer
-  arch_exclude:
-    # The thread analyzer depends on !ARCH_POSIX
-    - posix
 tests:
   debug.thread_analyzer.printk:
     extra_configs: