ci: use string @var@ instead of $var for lava job template

This helps to understand that the actual interpolation process cannot use
syntax like bash/sh. In addition, putting the @ sigil at both ends so that
@FOO_BAR is not incorrectly replaced as well.

Signed-off-by: Chase Qi <chase.qi@linaro.org>

.oniro-ci/test-generic.yaml

@@ -40,12 +40,12 @@
     # Get the job definition from remote source.
     - curl --silent "$CI_LAVA_JOB_DEFINITION" > job_def.yaml
     # Update the job definition with CI data.
-    - sed -i -e 's/$ci_job_id/'"$CI_JOB_ID"'/'
-      -e 's/$ci_project_id/'"$CI_PROJECT_ID"'/'
-      -e 's/$ci_pipeline_id/'"$CI_PIPELINE_ID"'/'
-      -e 's,$ci_pipeline_url,'"$CI_PIPELINE_URL"','
-      -e 's/$build_job_id/'"$build_job_id"'/'
-      -e 's,$callback_url,'"$CALLBACK_URL"',' job_def.yaml
+    - sed -i -e 's/@ci_job_id@/'"$CI_JOB_ID"'/'
+      -e 's/@ci_project_id@/'"$CI_PROJECT_ID"'/'
+      -e 's/@ci_pipeline_id@/'"$CI_PIPELINE_ID"'/'
+      -e 's,@ci_pipeline_url@,'"$CI_PIPELINE_URL"','
+      -e 's/@build_job_id@/'"$build_job_id"'/'
+      -e 's,@callback_url@,'"$CALLBACK_URL"',' job_def.yaml
     # Generate test jobs.
     - |
       set -x
@@ -55,14 +55,14 @@
         for image in $(find artifacts/images/${MACHINE} -name "*.elf" -exec basename {} \;); do
           image_basename=$(basename "${image}" ".elf")
           echo "--- Generating lava job definition ${image_basename}.yaml ---"
-          sed "s/\$image_basename/$image_basename/" job_def.yaml | tee lava_jobs/"${image_basename}".yaml
+          sed "s/@image_basename@/$image_basename/" job_def.yaml | tee lava_jobs/"${image_basename}".yaml
         done
       # Generate job definitions for linux LTP test.
       elif grep -q "\$TST_CMDFILES" job_def.yaml; then
         for test_cmdfile in ${LTP_TST_CMDFILES}; do
           ltp_job_name="ltp-${test_cmdfile}.yaml"
           echo "--- Generating lava job definition ${ltp_job_name} ---"
-          sed "s/\$TST_CMDFILES/${test_cmdfile}/" job_def.yaml | tee lava_jobs/"${ltp_job_name}"
+          sed "s/@TST_CMDFILES@/${test_cmdfile}/" job_def.yaml | tee lava_jobs/"${ltp_job_name}"
         done
       else
         mv job_def.yaml lava_jobs/