twister: Platform key for test suites

Adds an option to inform twister a testsuite should only be built and
run for platforms with unique sets of attributes. This enables
for example keying on unique (arch, simulation) platforms to run the test
suite on.

The most common usage may be test suites configured to run once per
(arch, simulation) pair as being enough. Additional information about
platforms may enable running a test once per hardware IP block or once
per soc family or soc avoiding duplicated effort in building and running
tests when once suffices.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>

scripts/schemas/twister/testsuite-schema.yaml

@@ -115,6 +115,12 @@ mapping:
         required: false
         sequence:
           - type: str
+      "platform_key":
+        required: false
+        type: seq
+        matching: "all"
+        sequence:
+          - type: str
       "tags":
         type: str
         required: false
@@ -272,6 +278,12 @@ mapping:
             required: false
             sequence:
               - type: str
+          "platform_key":
+            required: false
+            type: seq
+            matching: "all"
+            sequence:
+              - type: str
           "tags":
             type: str
             required: false