No way to tweak the cache parameters of an oembed request

oembedcore.module allows you to change an oembed request before it goes out (hook_oembed_request_alter), but the cache properties are difficult to change because there's no point where you can alter the oembedcore_render_cache object. For example, if I wanted to set oembed API request caches to CACHE_PERMANENT, I really have no good way of doing that.

If I want to force cache lifetimes on the embed markup cache or the thumbnail, then I can add a decorator to media_oembed_file_formatter_media_oembed_view to do that, but the same isn't true of the actual outgoing API request.

There is a variable that can be set to increase cache lifetimes when not set, but I can't set CACHE_PERMANENT there, because the value is added to REQUEST_TIME, not taken as absolute.

There are also cases where you would want to manipulate the cache keys.

The attached patch aims to make these elements alterable.