[ci] Continue application tests after one of them fails

The purpose of this change is to:
1. Provide more information to the developer who goes to look at CI results.
2. Help CI workflows complete faster, taking into account that we often restart these workflows.

Default strategy is `fail-fast: true`, so when one of app test fails,
all running jobs are canceled. This way we don't know if they would
succeed or not. And when we restart them, all progress is lost.

Reference:
* https://docs.github.com/en/actions/how-tos/write-workflows/choose-what-workflows-do/run-job-variations#handling-failures
* https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#jobsjob_idstrategyfail-fast

Signed-off-by: Nick Volynkin <nick.volynkin@gmail.com>

.github/workflows/pull-requests.yaml

@@ -269,6 +269,7 @@ jobs:
 
   test_apps:
     strategy:
+      fail-fast: false
       matrix: ${{ fromJson(needs.detect_test_matrix.outputs.matrix) }}
     name: Test ${{ matrix.app }}
     runs-on: [self-hosted]