feat: add command to get aggregate report

[infinitewarp]

Relates to JIRA: DISCOVERY-611

This PR adds a new aggregate subcommand under report.

❯ poetry run qpc report aggregate --help
usage: qpc report aggregate [-h] (--scan-job SCAN_JOB_ID | --report REPORT_ID)

options:
  -h, --help            show this help message and exit
  --scan-job SCAN_JOB_ID
                        Scan job identifier.
  --report REPORT_ID    Report identifier.

Given an apropriate scan job ID or report ID, it simply retrieves and outputs the requested aggregate report.

❯ poetry run qpc report aggregate --report 15 | head
{
    "ansible_hosts_all": 200,
    "ansible_hosts_in_database": 100,
    "ansible_hosts_in_jobs": 200,
    "inspect_result_status_failed": 0,
    "inspect_result_status_success": 0,
    "inspect_result_status_unknown": 601,
    "inspect_result_status_unreachable": 0,
    "instances_hypervisor": 0,
    "instances_physical": 0,

This command has no custom output formatting options. This command simply prints to stdout the JSON response returned by the server using qpc's existing pretty_format function.

❯ poetry run qpc report aggregate --scan-job 1701
Scan Job 1701 does not exist.

As discussed with Justin, we are not yet updating the man page to document this new feature. We may revisit that decision and update docs later.