thorvg: Update to 0.13.3, add webp loader

[akien-mga]

Remove embedded png loader, we use the external (libpng) one.

Release notes:

• https://github.com/thorvg/thorvg/releases/tag/v0.13.0
• https://github.com/thorvg/thorvg/releases/tag/v0.13.1
• https://github.com/thorvg/thorvg/releases/tag/v0.13.2
• https://github.com/thorvg/thorvg/releases/tag/v0.13.3

Note: Doesn't fix- #91781.

Bugsquad edit, closes: #90371

[akien-mga]

CC @capnm @MewPurPur

[Maran23]

Also worth checking if this fixes/has something to do with: #88165

[akien-mga]

Also worth checking if this fixes/has something to do with: #88165

I tried, doesn't seem to impact this.

[Maran23]

I tried, doesn't seem to impact this.

Thanks for checking! I will do a bisect to check where this regression came from.

[fire]

I imported the test case from #90371 and it did not crash.

This is a basic test and does not go into depth with technical review of thorvg.