GCP IAM Policies

[Bobi-Wan]

What this PR does / why we need it:
This PR is needed to track principal IAM permissions.
How this is done by collection every known project's IAM Policy, which contains all the role-member (principal) bindings.

As the GCP follows the following structure:
Org
->Folder1
->FolderX
->Project

IAM access is inherited if it is defined on a higher level.
The collected policy seems to include the roles that come from higher levels, so we don't need to collect those separately.

The collected structures are:

• IAMPolicy - same as GCP IAM Policy
• IAMBinding - a role:member (1:n) mapping inside a policy. There can be many bindings in a policy.
• IAMRoleMember - custom abstraction to be able to more easily query information about a principal.

The following tables were created respectively:

• gcp_iam_policy
• gcp_iam_binding
• gcp_iam_role_member

This PR is missing Grafana dashboards, but they will need to be discussed further, to be added the coming days.

Release note:

GCP IAM Policy

[dnaeon]

/lgtm