Revert "[gn] Split :pdf and :xps from :skia"

This reverts commit 3f34cf7c2d940a9ed84bf131d6c33b7380e180a0.

Reason for revert: breaking Android

Original change's description:
> [gn] Split :pdf and :xps from :skia
>
> After https://skia-review.googlesource.com/c/skia/+/1008277/2, we end up
> with an implicit dependency cycle:
>
> :skia -> :pdf/:xps (SkClipStack_AsPath) -> //modules/pathops -> :skia
>
> To fix, remove pdf and xps deps from "core" :skia and add to leaf apps
> instead.
>
> Change-Id: Ibdd58a97672ab5f9566c71907ce9e664eb809d4a
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1009616
> Reviewed-by: Ben Wagner <bungeman@google.com>
> Commit-Queue: Florin Malita <fmalita@google.com>

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I259449122b1b77894e841d3146487f5be8bebfba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1011517
Auto-Submit: Florin Malita <fmalita@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
3 files changed