Read SAST template and .gitlab-ci.yml to know about different variables related to analyzers

In this work, we need to add the functionality to read different environment variables related to a particular analyzer. We need to parse SAST template and .gitlab-ci.yml files to gather information about different variables related to analyzers.

For the first iteration, we will only support the following variables (documentation)

• SAST_BANDIT_EXCLUDED_PATHS
• SAST_BRAKEMAN_LEVEL
• SAST_FLAWFINDER_LEVEL
• SAST_GOSEC_LEVEL

Note: We do not store a value for these variables in our SAST vendored template, but some of them do have defaults. These defaults will be stored in sast_ui_schema.json