Paapi: add some browser features to request

[patmmccann]

Open to proposals as to where to put this stuff

see https://github.com/WICG/turtledove/pull/1156/files#diff-d753e360211de3733d3c03bfb5f53bda89db2065bd111cef3938d1f48d6c44f1

"Getting browser-side detectable features as an object: Sometimes it's desirable to get status of all features detectable via queryFeatureSupport in a forward-compatible way. Sufficiently recent versions provide this functionality via queryFeatureSupport('*'), which returns a dictionary describing state of various features. Since that functionality isn't available in older versions, backwards-compatibility polyfilling is suggested:

let qfs = navigator.protectedAudience ? navigator.protectedAudience.queryFeatureSupport.bind(navigator.protectedAudience) : null;

let allFeatureStatus = qfs ? (qfs("*") || { adComponentsLimit: qfs("adComponentsLimit"), deprecatedRenderURLReplacements: qfs("deprecatedRenderURLReplacements"), reportingTimeout: qfs("reportingTimeout") }) : {} An example return value would be:

{ "adComponentsLimit":40, "deprecatedRenderURLReplacements":false, "reportingTimeout":true, "permitCrossOriginTrustedSignals":true }"

Open concern: limiting the growth of this object

[patmmccann]

asked the chrome team live for tell us about features experimental since x version or something to cap the list at wicg call, they seemed open to the idea

[dmdabbs]

asked the chrome team live for tell us about features experimental since x version or something to cap the list at wicg call, they seemed open to the idea

@rdgordon-index reiterated that in today's FLEDGE call.

Other settings to consider: the k-anon enforced flag: https://github.com/WICG/turtledove/issues/867#issuecomment-2073916461

a "can load fenced frames" navigator property that is coming: https://github.com/WICG/turtledove/pull/1205