Convert Resizing FFs to a single one with OPS type

Context

Currently, we control the Image Resizing feature with two separate FFs:

• dynamic_image_resizing_requester
• dynamic_image_resizing_owner

It allowed us to perform a gradual rollout and test the performance of the feature in prod: #233704 (closed)

Goal

We still want to have the ability to disable the Resizing Feature easily, if there will be some issue, and we want to keep this for a long time.

We want to have a separate Feature Flags with an ops type, as this will fit into our FF managing schema.
Also, we want this flag to be enabled by default.

Notes

Enabling the flag by default means that the Image Resizing will be active for any self-managed instance.
We need to verify it won't cause any performance issue (see the separate issue under this epic - to be created).