[SVG] Rename `SVGResourceDocumentCache` to `SVGDocumentResourceTracker`

As part of CL:6807690, `SVGResourceDocumentCache` has transitioned
from functioning as a traditional cache to serving as a resource
tracker. Its primary role now is to assist `MemoryCache` in monitoring
and managing SVG resources more effectively. In this CL, we rename
`SVGResourceDocumentCache` to `SVGDocumentResourceTracker` to
reflect this change.

Bug: 360599258,348598125
Change-Id: I6f93c4103050734d5e80e9003ba170a1ba0bb51a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6972917
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Divyansh Mangal <dmangal@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1519376}