Proper results output handling for multiple SA having access to the same project_id

**Is your feature request related to a problem? Please describe.**
We are currently dumping results per [project_id](https://github.com/google/gcp_scanner/blob/4c416d7c889708e7e01bad5f92339c802135165f/src/gcp_scanner/scanner.py#L173C18-L173C18). However, if two SA have access to the same project, we will have two files for the same project from two different identities.

**Describe the solution you'd like**
We can either add service account name in the name of the file or merge same projects info into one file. The latter solution requires us to change timestamp in the name of the file.

**Describe alternatives you've considered**
We can leave it as it is now and avoid changing anything. User has information about identity that was used to query the file in the output.