Letting custom logo uploads under partner management section

[ramyaragupathy]

As part of partners management, admins should be allowed to upload custom logos through the partner management section. We could use the same storage option that is used for imagery upload in the project comments section.

cc @royallsilwallz @manjitapandey @emi420 @dakotabenjamin @nicolelaine

[dakotabenjamin]

We can use https://github.com/hotosm/tasking-manager/blob/develop/backend/api/system/image_upload.py for handling the upload, similar to adding org logos.