Add raw support for sending trigger variables

What does this MR do and why?

This MR adds the expand/raw support for variables forwarded by trigger jobs.

Step	Status
Add expand syntax to CI config	!98420 (merged)
Implement expand/raw logic for basic jobs	!102536 (merged)
Add QA test for raw variables in CI config YAML	!103181 (merged)
Use expand/raw logic for variables passed by bridge/trigger	<- HERE
Add documentation and CI schema for expand/raw	!103313 (merged)

Related to #353991 (closed)

Screenshots or screen recordings

Configs

# .gitlab-ci.yml

child:
  variables:
    VAR1: "PROJECTID-$CI_PROJECT_ID"
    VAR2: "PIPELINEID-$CI_PIPELINE_ID and $VAR1"
    VAR3:
      value: "PIPELINEID-$CI_PIPELINE_ID and $VAR1"
      expand: false
  trigger:
    include: .child-pipeline.yml

# .child-pipeline.yml

child_test:
  script:
    - echo $VAR1
    - echo $VAR2
    - echo $VAR3

Before enabling ci_raw_variables_in_yaml_config

After enabling ci_raw_variables_in_yaml_config

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.