Implementation of gaussian blur and box blur and raster node category

[calvintvu]

Closes #995

Implements both gaussian and box blurs under raster category

Screen.Recording.mp4

[calvintvu]

Typo in commit message

[Keavon]

I'll try to review this tomorrow.

[TrueDoctor]

Is there a specific reason why you chose to convert this to an image data type first instead of using or inbuilt one? Also @Keavon should blur happen in srgb or linear? They should give different results, so we have to think about which one is correct / what is compatible with other tools

[TrueDoctor]

It also looks like the current implementation quantizes the values to 8 bit which is most likely not what we want. We should also take SIMD friendliness into account here and potentially try to re-enable that target flag and hope that the chrome bug from two years ago has been fixed

[Keavon]

We should have both linear and gamma, with linear as default. https://www.youtube.com/watch?v=LKnqECcg6Gw

[calvintvu]

I've updated it to convert from linear/nonlinear before/after blurring using the functions from graphene_core::raster::Channel and changed from u8 values to f32

[Keavon]

Thanks. In the future, could you please add your followup work as additional commits instead of amending the original commit, so it's possible to compare them?

[calvintvu]

Yes ill keep that in mind

[Keavon]

A couple code review notes before I do a proper code review:

• You're repeating a whole lot of code by doing X then Y without reusing the logic, please do a self-review pass keeping DRY in mind
• Please replace whole-number decimals so they end in a decimal point (.) instead of point-zero (.0), per our style guide
• Run cargo clippy