WIP fix(fabric.Object): render clipPaths sharper

[asturur]

This is an issue we have since 2.4.0, clipPaths don't scale up well with object.
The issue, that is also a lesson, is that with the first round of clipPath release we added too many features ( nested clippaths, absolute clippaths, group of clipPaths ) and we thought we would fix the sharpness later.
Fixing the sharpness and keeping things working is hard, this has been in my to do list for long, i m not sure how to completely solve it and this is just a start.

I need to write a bunch of tests for regression since the one we have are not that much extensive

close #5494

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ShaMan123]

This PR has moved to the top of my list.
I think cache canvas needs attention not only for clip paths.
Take a look:

[ShaMan123]

What am I missing?
These are custom objects. I don't understand how to get them to render sharper.
The blue object uses an internal text object. I don't understand how to make it sharper.
The math object uses an image. How can fabric take care of scaling images so they render sharper?
Is this related to this PR?

[asturur]

no is not strictly realted. But if you want to share one at time, the source code of those custom objects, we can understand what is going on. If you can't disclose, you can send them privately,

[asturur]

replaced by #9774