Update mobile SDK integration guides to match current source

[jaredlockhart]

The mobile SDK integration guides have several gaps and outdated content compared to the current source in application-services:

Removed API still documented:

• globalUserParticipation no longer exists — split into experimentParticipation (experiments only) and rolloutParticipation (rollouts only)

Missing from integration guides:

• recordedContext NimbusBuilder option for behavioral targeting and Glean recording
• recordMalformedConfiguration(featureId, partId) for reporting invalid feature configs
• HardcodedNimbusFeatures testing helper class for unit/UI testing

Outdated examples:

• Complete NimbusBuilder examples missing recordedContext and featureManifest
• iOS example still uses deprecated customTargetingAttributes