ci: twister: Use output parameter file

This commit updates the workflow to use the output parameter file
(`GITHUB_OUTPUT`) instead of the stdout-based output parameter setting,
which is now deprecated by GitHub and will be removed in the near
future.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

.github/workflows/twister.yaml

@@ -100,8 +100,8 @@ jobs:
           else
             size=0
           fi
-          echo "::set-output name=subset::${subset}";
-          echo "::set-output name=size::${size}";
+          echo "subset=${subset}" >> $GITHUB_OUTPUT
+          echo "size=${size}" >> $GITHUB_OUTPUT
 
   twister-build:
     runs-on: zephyr_runner
@@ -171,7 +171,7 @@ jobs:
           string(TIMESTAMP current_date "%Y-%m-%d-%H;%M;%S" UTC)
           string(REPLACE "/" "_" repo ${{github.repository}})
           string(REPLACE "-" "_" repo2 ${repo})
-          message("::set-output name=repo::${repo2}")
+          file(APPEND $ENV{GITHUB_OUTPUT} "repo=${repo2}\n")
 
       - name: use cache
         id: cache-ccache