Make it easier to upgrade from ancient (pre v0.9.0) controllers

[mkmik]

by embracing strong backward compatibility and switching back accept-deprecated-v1-data to true by default.

Rationale

While sealed-secrets is a tool in many people's tool boxes, it's a rather "invisible" tool.

It stays there, does it's job and people focus on other things, often for years before putting back the spotlight on sealed secrets (usually when installing a new cluster etc). A 1yo version may appear ancient for us maintainers, but we do have
people out there running those versions, and we should make it easier (not harder!) for people to upgrade.

Furthermore, sealed-secrets's support is best effort and backward compatibility is a good idea if it can reduce the amount of questions by confused users who just happen to have to install sealed secrets in a new clusters, after having used a >2y old version in a previous cluster with no problems.