Renames the Base terraform template jobs for better scaling

What does this MR do?

Renames the jobs of the Base terraform template. The current jobs have very generic names that can easily clash with other jobs, and make it hard to understand what they cover.

Current example:

include:
  - template: Terraform/Base.latest.gitlab-ci.yml

myjob:
  extends: .init

New example:

include:
  - template: Terraform/Base.latest.gitlab-ci.yml

myjob:
  extends: .terraform:init

The new syntax helps the user to understand what the job is about even months after it was written.

As this is a breaking change, the changes are introduced in the "latest" template only. This requires a new "stable" Base template too that is added as part of the MR.

Manual QA project

https://gitlab.com/nagyv-gitlab/qa-for-mr-67719

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team