Expose the raw attribute of ci-variables models

What does this MR do and why?

This MR is not ready to merge because there are still some ci_job_variables.raw=true rows. !100705 (merged) is a requirement for this MR.

We did not expose the raw attribute of these tables:

• ci_pipeline_variables
• ci_group_variables
• ci_instance_variables
• ci_job_variables
• ci_pipeline_schedule_variables
• ci_variables

With this MR, this attribute is started to expose to Runner if assigned to true.

Related to #374616 (closed)

Step	MR
1. Remove and add the raw attribute again	!98527 (merged)
2. Fix ci_job_variables.raw (!98527 (comment 1126894456))	!100705 (merged)
3. (Optional) Change the logic of to_runner_variable to support raw.	<-- HERE

Screenshots or screen recordings

There is no raw IS TRUE on the tables:

• ci_pipeline_variables: https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/12642/commands/44605
• ci_group_variables: https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/12642/commands/44596
• ci_instance_variables: https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/12642/commands/44597
• ci_job_variables: https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/12642/commands/44601
• ci_pipeline_schedule_variables: https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/12642/commands/44598
• ci_variables: https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/12642/commands/44599

MR acceptance checklist

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