Mock pre-main-jh as scheduled and maintenance

Related issue: https://jihulab.com/gitlab-cn/gitlab/-/issues/2715

What does this MR do and why?

For scheduled and maintenance pipeline on main-jh, will trigger a lot of cache jobs.

If we want to trigger cache jobs on pre-main-jh branch, we should mock the variables on pre-main-jh branch.

For example:

update-static-analysis-cache is not triggered on pre-main-jh branch pipelines due to rule of :

if: $CI_PIPELINE_SOURCE == "schedule" && $SCHEDULE_TYPE == "maintenance"

update-static-analysis-cache:
  retry:
    max: 2
    when:
    - api_failure
    - data_integrity_failure
    - runner_system_failure
    - scheduler_failure
    - stuck_or_timeout_failure
    - unknown_failure
  before_script:
  - - echo $FOSS_ONLY
    - '[ "$FOSS_ONLY" = "1" ] && rm -rf ee/ qa/spec/ee/ qa/qa/specs/features/ee/ qa/qa/ee/
      qa/qa/ee.rb'
    - export GOPATH=$CI_PROJECT_DIR/.go
    - mkdir -p $GOPATH
    - source scripts/utils.sh
  - source scripts/prepare_build.sh
  extends:
  - ".static-analysis-base"
  - ".rubocop-job-cache-push"
  - ".shared:rules:update-cache"
  stage: prepare
  needs: []
  variables:
    SETUP_DB: 'false'
    ENABLE_SPRING: '1'
    BROWSERSLIST_IGNORE_OLD_DATA: 'true'
    GRAPHQL_SCHEMA_APOLLO_FILE: tmp/tests/graphql/gitlab_schema_apollo.graphql
  cache:
  - key: ruby-gems-debian-${DEBIAN_VERSION}-ruby-${RUBY_VERSION}
    paths:
    - vendor/ruby/
    policy: pull
  - key: rubocop-debian-${DEBIAN_VERSION}-ruby-${RUBY_VERSION}
    paths:
    - tmp/rubocop_cache/
    policy: push
  rules:
  - if: $CI_PIPELINE_SOURCE == "schedule" && $SCHEDULE_TYPE == "maintenance"
  - if: $CI_PROJECT_NAMESPACE == "gitlab-org/security" && $CI_PIPELINE_SOURCE == "schedule"
  - if: $CI_PROJECT_PATH == "gitlab-org/gitlab-foss" && $CI_PIPELINE_SOURCE == "schedule"
  - if: "$CI_MERGE_REQUEST_LABELS =~ /pipeline:update-cache/"
  script:
  - run_timed_command "fail_on_warnings bundle exec rake rubocop:check:graceful"

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