Add more information to COEP reporting

[yutakahirano]

• "destination", proposed by @arturjanc at Modify CORP for COEP reporting WICG/cross-origin-embedder-policy#9 (comment)
• "disposition", proposed by @clelland at https://chromium-review.googlesource.com/c/chromium/src/+/2074177/9/content/browser/net/cross_origin_embedder_policy_reporter.cc#32

[annevk]

Both of those seem safe in that they don't leak any information an attacker wouldn't already know.

[domenic]

This seems relatively easy to add to #5454, although perhaps it would be simpler to delay any normative changes until we can fully turn down the https://wicg.github.io/cross-origin-embedder-policy/ document.