using set_stats with large amounts of data slows down UI and API endpoints

[ryanpetrello]

1. Create an inventory w/ 25+ (local connection) hosts.
2. Run this playbook w/ a 100MB artifact file for set_stats:

---
- hosts: all
  connection: local
  tasks:
  - set_stats:
      data:
        random_data: "{{ lookup('file', 'random_data.txt') }}"
    delegate_to: localhost

bash-4.4$ base64 /dev/urandom | head -c 100000000 > random_data.txt
bash-4.4$ du -h random_data.txt
96M	random_data.txt

3. Go to /api/v2/inventories/N/hosts/
4. Become very, very sad:

[one-t]

Tested using a slightly modified example playbook on a local k8s install.

---
- hosts: all
  connection: local
  tasks:
  - shell: 'base64 /dev/urandom | head -c 100000000 > random_data.txt'
    run_once: true
  - set_stats:
      data:
        random_data: "{{ lookup('file', 'random_data.txt') }}"
    delegate_to: localhost

This is now working as expected, response times were around 0.05 seconds, which is normal for this installation.