Remove kDocumentDomain Permissions and Document Policy.

These policies were meant as a mechanism to deprecate setting
document.domain. The same goal is now being pursued with a different
mechanism, the Origin-Agent-Cluster http header. Due to this new solution these policies no longer serve a purpose and their support code can be removed.

Ref: https://groups.google.com/a/chromium.org/g/blink-dev/c/_oRc19PjpFo
Bug: 1344527
Change-Id: I8fc6886d3bf126e6939f6601b7befa56cb0f56b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3930823
Commit-Queue: Daniel Vogelheim <[email protected]>
Reviewed-by: Kent Tamura <[email protected]>
Reviewed-by: Arthur Sonzogni <[email protected]>
Reviewed-by: Xiaocheng Hu <[email protected]>
Reviewed-by: Mike West <[email protected]>
Reviewed-by: Ian Clelland <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1075782}