Add cpp-gitlab-advanced-sast to SAST templates and update docs

What does this MR do and why?

This MR turns on CPP Advanced SAST by adding the cpp-gitlab-advanced-sast job to both ci/templates/Jobs/SAST.gitlab-ci.yml and ci/templates/Jobs/SAST.latest.gitlab-ci.yml.

This MR also updates the documentation, which was already approved in Update Advanced SAST documentation for C/C++ fl... (!208059 - closed) • Hua Yan • 18.6, but is included here to keep the SAST CI/CD templates and the documentation in sync.

References

clangsa-sast: add to SAST CI/CD template (#533894 - closed) • Hua Yan • 18.6

clangsa-sast: update user facing documentation (#533892 - closed) • Hua Yan • 18.6

Screenshots or screen recordings

The added gitlab-advanced-sast-cpp jobs were successfully triggered.

How to set up and validate locally

Tested in

• (Do not merge) Use ci template to enable clangsa (gitlab-org/security-products/demos/experiments/clangsa/highway!16 - closed) • Unassigned (for SAST.gitlab-ci.yml) is obsolete due to product decisions that changed the job name

  new test for SAST.gitlab-ci.yml:

  (Do not merge) Demonstrate using SAST CI/CD tem... (gitlab-org/security-products/demos/experiments/cpp-advanced-sast/highway!10) • Unassigned

• (Do not merge) Use ci template (latest) to enab... (gitlab-org/security-products/demos/experiments/clangsa/highway!17 - closed) • Hua Yan (for SAST.latest.gitlab-ci.yml) is obsolete due to product decisions that changed the job name

  new test for SAST.latest.gitlab-ci.yml:

  (Do not merge) Demonstrate using the latest SAS... (gitlab-org/security-products/demos/experiments/cpp-advanced-sast/highway!11) • Unassigned

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