fix: 500 error during opening program certificate page (Quince)

[DmytroAlipov]

This is backport from the master.

Description:

Error 500 occurs when going to the Program certificate page if an organization is connected to the Authoring organizations field with an empty field Certificate logo image:

---

Steps to Reproduce:

1. The program is created.
2. In the Discovery admin panel, connect an organization in the Authoring organizations field that does not have an image loaded for the Certificate logo image field:

3. Earn a program certificate as a user.
4. Go to the program certificate page.

I propose that before saving the program, verify if the Certificate logo image field of the associated organizations is empty. Also, make the certificate_logo_image field required to be filled in the admin panel, but not in the model, to prevent unnecessary migrations.

On the Program page https://<discovery>/admin/course_metadata/program/:

On the Organization page https://<discovery>/admin/course_metadata/organization/:

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[mphilbrick211]

Hi @openedx/2u-phoenix! This is ready after the master is merged.

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