nvs: add long ci test for power off recovery and coverage

This test can be triggered manually:
`bot test name: test_nvs_coverage`

.gitlab-ci.yml

@@ -243,6 +243,24 @@ test_nvs_on_host:
     - cd components/nvs_flash/test_nvs_host
     - make test
 
+test_nvs_coverage:
+  stage: test
+  image: $CI_DOCKER_REGISTRY/esp32-ci-env$BOT_DOCKER_IMAGE_TAG
+  tags:
+    - nvs_host_test
+  dependencies: []
+  artifacts:
+    paths:
+      - components/nvs_flash/test_nvs_host/coverage_report
+  only:
+    - triggers
+  # This job takes a few hours to finish, so only run it on demand
+  variables:
+    BOT_NEEDS_TRIGGER_BY_NAME: 1
+  script:
+    - cd components/nvs_flash/test_nvs_host
+    - make coverage_report
+
 test_partition_table_on_host:
   stage: test
   image: $CI_DOCKER_REGISTRY/esp32-ci-env$BOT_DOCKER_IMAGE_TAG